Introduction
By the state-operator correspondence, the thermal partition function of a C F T d \mathrm{CFT}_d CFT d on a twisted S d − 1 × S 1 S^{d-1} \times S^1 S d − 1 × S 1
Z ( β ; ω i ) : = Tr S d − 1 e − β ( D − ω 1 J 1 − ⋯ − ω κ J κ ) , κ : = ⌊ d 2 ⌋ (1) Z(\beta;\omega_i) := \operatorname{Tr}_{S^{d-1}} e^{-\beta(D-\omega_1J_1-\cdots-\omega_\kappa J_\kappa)}, \qquad\kappa:= \left\lfloor\frac{d}{2}\right\rfloor \tag*{(1)} Z ( β ; ω i ) := Tr S d − 1 e − β ( D − ω 1 J 1 − ⋯ − ω κ J κ ) , κ := ⌊ 2 d ⌋ (1)
fully encodes the scaling dimensions Δ \Delta Δ , spins J i J_i J i and degeneracies of all local operators. While the detailed structure of Z ( β ; ω i ) Z(\beta;\omega_i) Z ( β ; ω i ) depends sensitively on the particular CFT, it was shown almost two decades ago [1 ] that its high-temperature behavior always takes the hydrodynamic form
ln Z = c ′ β d − 1 ∏ i = 1 κ ( 1 − ω i 2 ) + O ( β 3 − d ) , β → 0 + , ω i fixed . (2) \ln Z = \frac{c'}{\beta^{d-1}\prod_{i=1}^{\kappa}(1-\omega_i^2)}+O\left(\beta^{3-d}\right),\qquad\beta\to0^+,\ \omega_i\ \text{fixed}. \tag*{(2)} ln Z = β d − 1 ∏ i = 1 κ ( 1 − ω i 2 ) c ′ + O ( β 3 − d ) , β → 0 + , ω i fixed . (2)
This remarkably universal result was subsequently rederived using the formalism of ‘equilibrium partition functions’ [2 , 3 , 4 ] , an approach that was further developed and named thermal effective theory in [5 ] .
A systematic analysis of subleading corrections to Eq. (2) was presented in the recent paper [6 ] . The analysis of [6 ] was largely performed in d = 4 d=4 d = 4 ; the generalization to CP-preserving1 CFTs in arbitrary even dimensions
d = 2 κ d=2\kappa d = 2 κ is presented below. One finds
ln Z = ln Z r o t + ln Z s h , \ln Z=\ln Z^{\mathrm{rot}}+\ln Z^{\mathrm{sh}}, ln Z = ln Z rot + ln Z sh ,
ln Z r o t = − 1 β d − 1 x 1 x 2 … x κ ( ∑ q = 0 ∞ β 2 q S q ( x i ) ) , \ln Z^{\mathrm{rot}}=-\frac{1}{\beta^{d-1}x_1x_2\ldots x_\kappa}\left(\sum_{q=0}^{\infty}\beta^{2q}S_q(x_i)\right), ln Z rot = − β d − 1 x 1 x 2 … x κ 1 ( q = 0 ∑ ∞ β 2 q S q ( x i ) ) ,
ln Z s h β = κ ! a 2 κ [ ( − 1 ) κ + 1 2 2 κ − 1 ∑ i = 1 κ ∫ 0 1 d s ∏ j = 1 j ≠ i κ ( s x i − 2 x j ) 2 x j ( x i − x j ) ] . (3) \frac{\ln Z^{\mathrm{sh}}}{\beta}=\kappa!a_{2\kappa}\left[(-1)^\kappa+\frac{1}{2^{2\kappa-1}}\sum_{i=1}^{\kappa}\int_0^1ds\prod_{\substack{j=1\\j\ne i}}^\kappa\frac{(sx_i-2x_j)^2}{x_j(x_i-x_j)}\right]. \tag*{(3)} β ln Z sh = κ ! a 2 κ ( − 1 ) κ + 2 2 κ − 1 1 i = 1 ∑ κ ∫ 0 1 d s j = 1 j = i ∏ κ x j ( x i − x j ) ( s x i − 2 x j ) 2 . (3)
ln Z s h \ln Z^{\mathrm{sh}} ln Z sh , the universal ‘anomalous shift’ of the partition function, is proportional to the a a a anomaly a 2 κ a_{2\kappa} a 2 κ .12 The ‘non-anomalous’ part, ln Z r o t \ln Z^{\mathrm{rot}} ln Z rot , is non-universal. It is characterized by the coefficient functions S q S_q S q , which turn out to be (not necessarily homogeneous) symmetric degree-q q q polynomials13 in the variables ω i 2 \omega_i^2 ω i 2 , or equivalently in
x i : = 1 − ω i 2 , ( i = 1 … κ ) . (4) x_i:=1-\omega_i^2,\qquad(i=1\ldots\kappa). \tag*{(4)} x i := 1 − ω i 2 , ( i = 1 … κ ) . (4)
While the polynomials S q S_q S q are theory dependent, their coefficients are constrained, by the locality of the thermal effective action, to obey several additional sharp universal constraints [6 ] . These constraints force S q S_q S q to lie in a d q d_q d q codimensional subspace [6 ] (of the space of arbitrary symmetric degree q q q polynomials), where d q d_q d q is defined by14
t κ ∏ i = 1 κ + 1 ( 1 − t i ) = ∑ q = 0 ∞ d q t q . (5) \frac{t^\kappa}{\prod_{i=1}^{\kappa+1}(1-t^i)}=\sum_{q=0}^{\infty}d_qt^q \, . \tag*{(5)} ∏ i = 1 κ + 1 ( 1 − t i ) t κ = q = 0 ∑ ∞ d q t q . (5)
at large q q q , d q ∼ q κ κ ! ( κ + 1 ) ! d_q\sim\frac{q^\kappa}{\kappa!(\kappa+1)!} d q ∼ κ ! ( κ + 1 )! q κ . While the precise form of the constraints on S q S_q S q was worked out in [6 ] at the first nontrivial value, q = κ q=\kappa q = κ , the detailed structure of the infinite tower of constraints at q ≥ κ + 1 q\geq\kappa+1 q ≥ κ + 1 was left undetermined. A central result of this paper is the following. The entire infinite tower of constraints is encapsulated, at every κ ≥ 2 \kappa\geq2 κ ≥ 2 , by a strikingly simple universal equation involving a Z κ + 1 \mathbb{Z}_{\kappa+1} Z κ + 1 action, generated by Ω \Omega Ω , which cyclically permutes the thermal circle and angular directions on S 2 κ − 1 × S 1 S^{2\kappa-1}\times S^1 S 2 κ − 1 × S 1 , via
Ω : ( b 0 , b 1 , … , b κ ) ⟶ ( b 1 , … , b κ , b 0 ) , \Omega:(b_0,b_1,\ldots,b_\kappa)\longrightarrow(b_1,\ldots,b_\kappa,b_0), Ω : ( b 0 , b 1 , … , b κ ) ⟶ ( b 1 , … , b κ , b 0 ) ,
where $(b_0,b_1,\ldots,b_\kappa):=(\beta,\beta\omega_1,\ldots,\beta\omega_\kappa).
{#eq:6}
Our central equation asserts the vanishing of the Z κ + 1 \mathbb{Z}_{\kappa+1} Z κ + 1 -invariant part of ln Z r o t β \frac{\ln Z^{\mathrm{rot}}}{\beta} β l n Z rot ,
( 1 + Ω + Ω 2 + … + Ω κ ) ∘ [ ln Z r o t β ] = 0. (6) (1+\Omega+\Omega^2+\ldots+\Omega^\kappa)\circ\left[\frac{\ln Z^{\mathrm{rot}}}{\beta}\right]=0. \tag*{(6)} ( 1 + Ω + Ω 2 + … + Ω κ ) ∘ [ β ln Z rot ] = 0. (6)
Eq. (6) , together with our (conjectured) expression for ln Z s h \ln Z^{\mathrm{sh}} ln Z sh , then implies
( 1 + Ω + Ω 2 + … + Ω κ ) ∘ [ ln Z β ] = ( − 1 ) κ κ ! a 2 κ . (7) (1+\Omega+\Omega^2+\ldots+\Omega^\kappa)\circ\left[\frac{\ln Z}{\beta}\right]=(-1)^\kappa\kappa!a_{2\kappa}. \tag*{(7)} ( 1 + Ω + Ω 2 + … + Ω κ ) ∘ [ β ln Z ] = ( − 1 ) κ κ ! a 2 κ . (7)
Our demonstration of Eq. (7) applies only in an order-by-order sense in β 2 \beta^2 β 2 . Eq. (7) is thus best viewed as a generating function for an infinite tower of constraints on coefficient polynomials (see Eq. (3) )
T q : = β 2 q S q , (8) T_q:=\beta^{2q}S_q, \tag*{(8)} T q := β 2 q S q , (8)
that are homogeneous of degree q q q in ( b 0 2 , b 1 2 , … , b κ 2 ) (b_0^2,b_1^2,\ldots,b_\kappa^2) ( b 0 2 , b 1 2 , … , b κ 2 ) . While T q T_q T q are symmetric under the interchange b i 2 ↔ b j 2 b_i^2\leftrightarrow b_j^2 b i 2 ↔ b j 2 for i , j ≠ 0 i,j\neq0 i , j = 0 , they are not necessarily invariant under permutations involving b 0 2 b_0^2 b 0 2 , and so can be rewritten (see Appendix A) as
T q = I q ( 0 ) + b 0 2 I q ( 1 ) + b 0 4 I q ( 2 ) + … + b 0 2 κ I q ( κ ) (9) T_q=I_q^{(0)}+b_0^2I_q^{(1)}+b_0^4I_q^{(2)}+\ldots+b_0^{2\kappa}I_q^{(\kappa)} \tag*{(9)} T q = I q ( 0 ) + b 0 2 I q ( 1 ) + b 0 4 I q ( 2 ) + … + b 0 2 κ I q ( κ ) (9)
where I q ( r ) I_q^{(r)} I q ( r ) is a completely symmetric polynomial of degree ( q − r ) (q-r) ( q − r ) in ( b 0 2 , b 1 2 , … , b κ 2 ) (b_0^2,b_1^2,\ldots,b_\kappa^2) ( b 0 2 , b 1 2 , … , b κ 2 ) and absent for r > q r>q r > q . Eq. (6) is equivalent to
I q ( κ ) = 0 , ∀ q ≥ κ , (10) I_q^{(\kappa)}=0,\quad\forall q\geq\kappa, \tag*{(10)} I q ( κ ) = 0 , ∀ q ≥ κ , (10)
effectively imposing d q d_q d q constraints on S q S_q S q , in agreement with the expectations described around Eq. (5) . We demonstrate the constraining power below explicitly for κ = 2 \kappa=2 κ = 2 and delegate the derivation of Eq. (10) for κ > 2 \kappa>2 κ > 2 to Appendix A and the SM, and the counting of constraints to Appendix D.
As a highly nontrivial check on the results of this paper, we verify that the partition function of Kerr-AdS2 κ + 1 _{2\kappa+1} 2 κ + 1 black holes15 obeys the central equation Eq. (7) as an exact non-perturbative identity between functions of ( b 0 2 , b 1 2 , … , b κ 2 ) (b_0^2,b_1^2,\ldots,b_\kappa^2) ( b 0 2 , b 1 2 , … , b κ 2 ) . In the rest of this paper, we first present details of our derivations for the simplest nontrivial dimension d = 4 d=4 d = 4 , and then sketch generalizations to arbitrary dimensions.
Derivation of the central equation
Simplifying the measure
As explained in [6 ] , the most general local thermal effective action for a d = 2 κ d=2\kappa d = 2 κ dimensional CFT takes the form Eq. (3) , with
ln Z r o t = ∫ d d x g ( υ 2 ) κ I . (11) \ln Z^{\mathrm{rot}}=\int d^dx\frac{\sqrt{g}}{(\upsilon^2)^\kappa}\mathcal{I}. \tag*{(11)} ln Z rot = ∫ d d x ( υ 2 ) κ g I . (11)
Specializing to d = 4 d=4 d = 4 , I \mathcal{I} I is a local Weyl invariant scalar constructed out of both the metric of S 3 × R S^3\times R S 3 × R
d s 2 = d τ 2 + d θ 2 + sin 2 θ d ϕ 1 2 + cos 2 θ d ϕ 2 2 , (12) ds^2=d\tau^2+d\theta^2+\sin^2\theta\,d\phi_1^2+\cos^2\theta\,d\phi_2^2, \tag*{(12)} d s 2 = d τ 2 + d θ 2 + sin 2 θ d ϕ 1 2 + cos 2 θ d ϕ 2 2 , (12)
as well as the ‘identification vector’
v = β ( ∂ τ − i ω 1 ∂ ϕ 1 − i ω 2 ∂ ϕ 2 ) = b 0 ∂ τ + b 1 ( − i ∂ ϕ 1 ) + b 2 ( − i ∂ ϕ 2 ) (13) v=\beta\left(\partial_\tau-i\omega_1\partial_{\phi_1}-i\omega_2\partial_{\phi_2}\right)
=b_0\partial_\tau+b_1(-i\partial_{\phi_1})+b_2(-i\partial_{\phi_2}) \tag*{(13)} v = β ( ∂ τ − i ω 1 ∂ ϕ 1 − i ω 2 ∂ ϕ 2 ) = b 0 ∂ τ + b 1 ( − i ∂ ϕ 1 ) + b 2 ( − i ∂ ϕ 2 ) (13)
which determines the boundary conditions of all dynamical fields χ \chi χ via
χ ( τ , ϕ 1 , ϕ 2 , θ ) = e L v χ ( τ , ϕ 1 , ϕ 2 , θ ) . (14) \chi(\tau,\phi_1,\phi_2,\theta)=e^{\mathcal{L}_v}\chi(\tau,\phi_1,\phi_2,\theta). \tag*{(14)} χ ( τ , ϕ 1 , ϕ 2 , θ ) = e L v χ ( τ , ϕ 1 , ϕ 2 , θ ) . (14)
Translational invariance allows the integrals over τ \tau τ , ϕ 1 \phi_1 ϕ 1 and ϕ 2 \phi_2 ϕ 2 to be evaluated. Changing integration variables from θ \theta θ to θ 6 \theta^6 θ 6
z : = β 2 ( 1 − x 1 x 2 γ 2 ) , (15) z:=\beta^2(1-x_1x_2\gamma^2), \tag*{(15)} z := β 2 ( 1 − x 1 x 2 γ 2 ) , (15)
where
γ 2 : = 1 1 − ω 2 2 + sin 2 θ ( ω 2 2 − ω 1 2 ) , \gamma^2:=\frac{1}{1-\omega_2^2+\sin^2\theta(\omega_2^2-\omega_1^2)}, γ 2 := 1 − ω 2 2 + sin 2 θ ( ω 2 2 − ω 1 2 ) 1 ,
we find (see around (S1) in SM)
g 4 ( v 2 ) 2 ∫ 0 β d θ ∫ 0 β d τ ∫ 0 2 π d ϕ 1 ∫ 0 2 π d ϕ 2 = β P d z , (16) \frac{\sqrt{g_4}}{(v^2)^2}\int_0^\beta d\theta\int_0^\beta d\tau\int_0^{2\pi}d\phi_1\int_0^{2\pi}d\phi_2=\beta P\,dz, \tag*{(16)} ( v 2 ) 2 g 4 ∫ 0 β d θ ∫ 0 β d τ ∫ 0 2 π d ϕ 1 ∫ 0 2 π d ϕ 2 = β P d z , (16)
where P : = 2 π 2 ( b 0 2 − b 1 2 ) ( b 1 2 − b 2 2 ) ( b 2 2 − b 0 2 ) P:=\frac{2\pi^2}{(b_0^2-b_1^2)(b_1^2-b_2^2)(b_2^2-b_0^2)} P := ( b 0 2 − b 1 2 ) ( b 1 2 − b 2 2 ) ( b 2 2 − b 0 2 ) 2 π 2 .
Eq. (12) can thus be rewritten as
ln Z r o t β = P ∫ b 1 2 b 2 2 d z I b 0 , b 1 , b 2 ( z ) . (17) \frac{\ln Z^{\mathrm{rot}}}{\beta}=P\int_{b_1^2}^{b_2^2}dz\,\mathcal{I}_{b_0,b_1,b_2}(z). \tag*{(17)} β ln Z rot = P ∫ b 1 2 b 2 2 d z I b 0 , b 1 , b 2 ( z ) . (17)
Notice that while P P P is antisymmetric under interchanges of b i 2 b_i^2 b i 2 and b j 2 b_j^2 b j 2 , it is symmetric under Z 3 \mathbb{Z}_3 Z 3 cyclical permutations. In (17) we have renamed I = I b 0 , b 1 , b 2 \mathcal{I}=\mathcal{I}_{b_0,b_1,b_2} I = I b 0 , b 1 , b 2 to emphasize the dependence of this function on the ‘compactification data’ ( b 0 , b 1 , b 2 ) (b_0,b_1,b_2) ( b 0 , b 1 , b 2 ) .
The Z 3 \mathbb{Z}_3 Z 3 invariance of I b 0 , b 1 , b 2 \mathcal{I}_{b_0,b_1,b_2} I b 0 , b 1 , b 2
As explained in [6 ] , Weyl invariance and locality together ensure that I \mathcal{I} I can be expressed as a total derivative plus a power series in the three local Weyl invariant scalars tr ( ω 2 ) \operatorname{tr}(\omega^2) tr ( ω 2 ) , v 2 S v^2S v 2 S and v 2 B μ ( ω 2 ) μ ν B ν v^2B_\mu(\omega^2)^{\mu\nu}B_\nu v 2 B μ ( ω 2 ) μν B ν (see [6 ] for definitions). The coefficients of this expansion are theory dependent but independent of the ‘compactification data’. As a consequence, I \mathcal{I} I depends on ( b 0 , b 1 , b 2 ) (b_0,b_1,b_2) ( b 0 , b 1 , b 2 ) only through the local Weyl invariant scalars. A straightforward computation reveals that
tr ( ω 2 ) 8 = z , v 2 S = b 0 2 + b 1 2 + b 2 2 − 3 z , \frac{\operatorname{tr}(\omega^2)}{8}=z,\qquad v^2S=b_0^2+b_1^2+b_2^2-3z, 8 tr ( ω 2 ) = z , v 2 S = b 0 2 + b 1 2 + b 2 2 − 3 z ,
v 2 B μ ( ω 2 ) μ ν B ν = − 4 ( z − b 0 2 ) ( z − b 1 2 ) ( z − b 2 2 ) . (18) v^2B_\mu(\omega^2)^{\mu\nu}B_\nu=-4(z-b_0^2)(z-b_1^2)(z-b_2^2). \tag*{(18)} v 2 B μ ( ω 2 ) μν B ν = − 4 ( z − b 0 2 ) ( z − b 1 2 ) ( z − b 2 2 ) . (18)
Note that each of the quantities in (18) is a polynomial both in z z z as well as in b i 2 b_i^2 b i 2 (see the discussion below (29) for a structural explanation of this feature). Each of the scalars listed in (18) , and so I b 0 , b 1 , b 2 \mathcal{I}_{b_0,b_1,b_2} I b 0 , b 1 , b 2 , is manifestly invariant under S 3 S_3 S 3 permutations of ( b 0 , b 1 , b 2 ) (b_0,b_1,b_2) ( b 0 , b 1 , b 2 ) , so that
I b 0 , b 1 , b 2 ( z ) = I b 1 , b 2 , b 0 ( z ) = I b 2 , b 0 , b 1 ( z ) = I ( z ) . (19) \mathcal{I}_{b_0,b_1,b_2}(z)=\mathcal{I}_{b_1,b_2,b_0}(z)=\mathcal{I}_{b_2,b_0,b_1}(z)=\mathcal{I}(z). \tag*{(19)} I b 0 , b 1 , b 2 ( z ) = I b 1 , b 2 , b 0 ( z ) = I b 2 , b 0 , b 1 ( z ) = I ( z ) . (19)
Derivation using Cauchy’s theorem
When d = 4 d=4 d = 4 , our central equation Eq. (7) abbreviates
3 S ∘ [ ln Z β ] = 2 a 4 , (20) 3\mathcal{S}\circ\left[\frac{\ln Z}{\beta}\right]=2a_4, \tag*{(20)} 3 S ∘ [ β ln Z ] = 2 a 4 , (20)
where S \mathcal{S} S is the Z 3 \mathbb{Z}_3 Z 3 symmetrization operator
S : = ( 1 + Ω + Ω 2 ) 3 . (21) \mathcal{S}:=\frac{(1+\Omega+\Omega^2)}{3}. \tag*{(21)} S := 3 ( 1 + Ω + Ω 2 ) . (21)
Since P P P is Z 3 \mathbb{Z}_3 Z 3 invariant, S ∘ P = P \mathcal{S}\circ P=P S ∘ P = P . Using (17)
3 P × S ∘ [ ln Z r o t β ] = 3 S ∘ [ ln Z r o t β × 1 P ] = ∫ b 1 2 b 2 2 d z I b 0 , b 1 , b 2 ( z ) + ∫ b 2 2 b 0 2 d z I b 1 , b 2 , b 0 ( z ) + ∫ b 0 2 b 1 2 d z I b 2 , b 0 , b 1 ( z ) = ∮ d z I ( z ) = 0. (22) \begin{aligned}
\frac{3}{P}\times\mathcal{S}\circ\left[\frac{\ln Z^{\mathrm{rot}}}{\beta}\right]=3\mathcal{S}\circ\left[\frac{\ln Z^{\mathrm{rot}}}{\beta}\times\frac{1}{P}\right] \\
&=\int_{b_1^2}^{b_2^2}dz\,\mathcal{I}_{b_0,b_1,b_2}(z)+\int_{b_2^2}^{b_0^2}dz\,\mathcal{I}_{b_1,b_2,b_0}(z) \\
&+\int_{b_0^2}^{b_1^2}dz\,\mathcal{I}_{b_2,b_0,b_1}(z) \\
&=\oint dz\,\mathcal{I}(z)=0. \tag*{(22)}
\end{aligned} P 3 × S ∘ [ β ln Z rot ] = 3 S ∘ [ β ln Z rot × P 1 ] = ∫ b 1 2 b 2 2 d z I b 0 , b 1 , b 2 ( z ) + ∫ b 2 2 b 0 2 d z I b 1 , b 2 , b 0 ( z ) + ∫ b 0 2 b 1 2 d z I b 2 , b 0 , b 1 ( z ) = ∮ d z I ( z ) = 0. (22)
∴ S ∘ [ ln Z r o t β ] = 0. \therefore\mathcal{S}\circ\left[\frac{\ln Z^{\mathrm{rot}}}{\beta}\right]=0. ∴ S ∘ [ β ln Z rot ] = 0.
The equality in the fourth line above follows order by order in β 2 \beta^2 β 2 ; since I \mathcal{I} I is a polynomial in z z z with coefficients that are polynomials in b i 2 b_i^2 b i 2 , the integral of each monomial over the closed contour [ b 1 2 , b 2 2 ] ∪ [ b 2 2 , b 0 2 ] ∪ [ b 0 2 , b 1 2 ] [b_1^2,b_2^2]\cup[b_2^2,b_0^2]\cup[b_0^2,b_1^2] [ b 1 2 , b 2 2 ] ∪ [ b 2 2 , b 0 2 ] ∪ [ b 0 2 , b 1 2 ] vanishes trivially. A simple computation also shows that
3 S ∘ ln Z s h β = 3 S ∘ [ a 4 12 ( x 1 x 2 + x 2 x 1 + 7 ) ] = 2 a 4 . (23) 3\mathcal{S}\circ\frac{\ln Z^{\mathrm{sh}}}{\beta}=3\mathcal{S}\circ\left[\frac{a_4}{12}\left(\frac{x_1}{x_2}+\frac{x_2}{x_1}+7\right)\right]=2a_4. \tag*{(23)} 3 S ∘ β ln Z sh = 3 S ∘ [ 12 a 4 ( x 2 x 1 + x 1 x 2 + 7 ) ] = 2 a 4 . (23)
Plugging Eq. (23) and Eq. (24) into the first of Eq. (3), we recover Eq. (21). In Appendix B we demonstrate that Eq. (21) simplifies at the special angular velocities ( ω 1 2 , ω 2 2 ) = ( e 2 π i 3 , e 4 π i 3 ) (\omega_1^2,\omega_2^2)=\left(e^{\frac{2\pi i}{3}},e^{\frac{4\pi i}{3}}\right) ( ω 1 2 , ω 2 2 ) = ( e 3 2 π i , e 3 4 π i ) , where it exactly reproduces Eq. (7) and Eq. (22) of [6 ] .
In Appendix C we present a physically intriguing rederivation of (19) that does not invoke the computational result (18) . Briefly, we construct a Z 3 \mathbb{Z}_3 Z 3 group of diffeomorphisms, which cyclically permute ( τ , i ϕ 1 , i ϕ 2 ) (\tau,i\phi_1,i\phi_2) ( τ , i ϕ 1 , i ϕ 2 ) , but leave the coordinate z z z invariant. These conformally map (see Figure 5 in SM)
Figure 5. The map from spheres to hyperbolic spaces
S 3 × R → Ω A d S 3 × S 1 → Ω A d S 3 ′ × S ′ 1 → Ω S 3 × R . (24) S^3\times R\xrightarrow{\Omega}AdS_3\times S^1\xrightarrow{\Omega}AdS'_3\times S'^1\xrightarrow{\Omega}S^3\times R. \tag*{(24)} S 3 × R Ω A d S 3 × S 1 Ω A d S 3 ′ × S ′1 Ω S 3 × R . (24)
where A d S 3 × S 1 AdS_3\times S^1 A d S 3 × S 1 and A d S 3 ′ × S ′ 1 AdS'_3\times S'^1 A d S 3 ′ × S ′1 are distinct. Remarkably, an analytic continuation in z z z turns each of the A d S × S 1 AdS\times S^1 A d S × S 1 spacetimes into S 3 × R S^3\times R S 3 × R , but with a cyclically permuted v v v vector. (19) then follows from the Weyl invariance of I \mathcal{I} I .
The vanishing of I q ( 2 ) \mathcal{I}^{(2)}_q I q ( 2 ) in d = 4 d=4 d = 4
We will now show that the small β 2 \beta^2 β 2 expansion of the constraint (6) on ln Z r o t \ln Z^{\mathrm{rot}} ln Z rot yields (10) in d = 4 d=4 d = 4 . The second line of Eq. (3) can be rewritten as 17
ln Z r o t β = − P 2 π 2 ∑ q = 0 ∞ ( b 2 2 − b 1 2 ) T q = − 1 2 π 2 ∑ q = 0 ∞ [ P I q ( 0 ) ( b 2 2 − b 1 2 ) + P I q ( 1 ) ( b 2 2 b 0 2 − b 1 2 b 0 2 ) + P I q ( 2 ) ( b 2 2 b 0 4 − b 1 2 b 0 4 ) ] , (25) \begin{aligned}
\frac{\ln Z^{\mathrm{rot}}}{\beta}=-\frac{P}{2\pi^2}\sum_{q=0}^{\infty}(b_2^2-b_1^2)T_q \\
&=-\frac{1}{2\pi^2}\sum_{q=0}^{\infty}\left[P I_q^{(0)}\left(b_2^2-b_1^2\right)+P I_q^{(1)}\left(b_2^2b_0^2-b_1^2b_0^2\right)+P I_q^{(2)}\left(b_2^2b_0^4-b_1^2b_0^4\right)\right], \tag*{(25)}
\end{aligned} β ln Z rot = − 2 π 2 P q = 0 ∑ ∞ ( b 2 2 − b 1 2 ) T q = − 2 π 2 1 q = 0 ∑ ∞ [ P I q ( 0 ) ( b 2 2 − b 1 2 ) + P I q ( 1 ) ( b 2 2 b 0 2 − b 1 2 b 0 2 ) + P I q ( 2 ) ( b 2 2 b 0 4 − b 1 2 b 0 4 ) ] , (25)
where we have used Eq. (9) . As P P P , I q ( 0 ) I_q^{(0)} I q ( 0 ) , I q ( 1 ) I_q^{(1)} I q ( 1 ) and I q ( 2 ) I_q^{(2)} I q ( 2 ) are all invariant under Z 3 \mathbb{Z}_3 Z 3 cyclical shifts,
3 S ∘ [ ln Z r o t β ] = 3 2 π 2 ∑ q = 0 ∞ [ { S ∘ ( b 1 2 − b 2 2 ) } P I q ( 0 ) + { S ∘ ( b 1 2 b 0 2 − b 2 2 b 0 2 ) } P I q ( 1 ) + { S ∘ ( b 1 2 b 0 4 − b 2 2 b 0 4 ) } P I q ( 2 ) ] = − ∑ q = 0 ∞ I q ( 2 ) . (26) \begin{aligned}
3\mathcal{S}\circ\left[\frac{\ln Z^{\mathrm{rot}}}{\beta}\right]=\frac{3}{2\pi^2}\sum_{q=0}^{\infty}\left[\{\mathcal{S}\circ\left(b_1^2-b_2^2\right)\}PI_q^{(0)}+\{\mathcal{S}\circ\left(b_1^2b_0^2-b_2^2b_0^2\right)\}PI_q^{(1)}+\{\mathcal{S}\circ\left(b_1^2b_0^4-b_2^2b_0^4\right)\}PI_q^{(2)}\right] \\
&=-\sum_{q=0}^{\infty}I_q^{(2)}. \tag*{(26)}
\end{aligned} 3 S ∘ [ β ln Z rot ] = 2 π 2 3 q = 0 ∑ ∞ [ { S ∘ ( b 1 2 − b 2 2 ) } P I q ( 0 ) + { S ∘ ( b 1 2 b 0 2 − b 2 2 b 0 2 ) } P I q ( 1 ) + { S ∘ ( b 1 2 b 0 4 − b 2 2 b 0 4 ) } P I q ( 2 ) ] = − q = 0 ∑ ∞ I q ( 2 ) . (26)
(The vanishing of the first two terms and the simplification of the last term follow from the identities Eq. (95) in the SM). Since I q ( 2 ) I_q^{(2)} I q ( 2 ) is homogeneous of degree ( q − 2 ) (q-2) ( q − 2 ) , we conclude that it must vanish for each q q q .
See around (S51) in SM for a generalization of this derivation to d = 2 κ d=2\kappa d = 2 κ , and Appendix D for a counting of these constraints.
Generalization to d = 2 κ d=2\kappa d = 2 κ dimensions for arbitrary κ \kappa κ
The generalization of our discussion to arbitrary even dimensions (see SM, between (S63) and (S157) for all details) proceeds in two steps.
We first express all local EFT terms using a common set of scalar variables. In the embedding space R 2 κ , 2 \mathbb{R}^{2\kappa,2} R 2 κ , 2 , boundary spacetime points are null rays N N N , while the CKV v v v corresponds to an adjoint SO ( 2 κ , 2 ) \operatorname{SO}(2\kappa,2) SO ( 2 κ , 2 ) matrix A A A . Using the geometrically natural coordinates
m ( a ) ≡ N ⋅ B a N N ⋅ B N , B = − A 2 , (27) m^{(a)}\equiv\frac{N\cdot B^aN}{N\cdot BN},\qquad B=-A^2, \tag*{(27)} m ( a ) ≡ N ⋅ B N N ⋅ B a N , B = − A 2 , (27)
we find that Eq. (11) becomes
( ln Z r o t β ) = ( − 1 ) κ 2 π κ V ∫ D 0 I \left(\frac{\ln Z^{\mathrm{rot}}}{\beta}\right)=\frac{(-1)^{\kappa}2\pi^{\kappa}}{\mathcal{V}}\int_{D_0}\mathcal{I} ( β ln Z rot ) = V ( − 1 ) κ 2 π κ ∫ D 0 I
I = d m 2 ∧ d m 3 … ∧ d m κ I ( E r , m ( a ) ) \mathcal{I}=dm_2\wedge dm_3\ldots\wedge dm_\kappa\,\mathcal{I}\left(E_r,m^{(a)}\right) I = d m 2 ∧ d m 3 … ∧ d m κ I ( E r , m ( a ) )
V = ∏ 0 ≤ i < j ≤ κ ( b j 2 − b i 2 ) (28) \mathcal{V}=\prod_{0\leq i<j\leq\kappa}\left(b_j^2-b_i^2\right) \tag*{(28)} V = 0 ≤ i < j ≤ κ ∏ ( b j 2 − b i 2 ) (28)
where E r E_r E r are defined in (A1), and the integration range D 0 D_0 D 0 is a simplex built out of the κ \kappa κ vectors
( p 0 b ) j = b 0 2 j − b b 2 j b 0 2 − b b 2 , ( b = 1 … κ ) . (29) (p_{0b})_j=\frac{b_0^{2j}-b_b^{2j}}{b_0^2-b_b^2},\qquad(b=1\ldots\kappa). \tag*{(29)} ( p 0 b ) j = b 0 2 − b b 2 b 0 2 j − b b 2 j , ( b = 1 … κ ) . (29)
In the Weyl frame defined by the condition N ⋅ B N = − 1 N\cdot BN=-1 N ⋅ B N = − 1 , the variables m ( a ) m^{(a)} m ( a ) are polynomial in N N N and B B B . In this Weyl frame, the projector Π \Pi Π onto the CFT submanifold of R 2 κ , 2 \mathbb{R}^{2\kappa,2} R 2 κ , 2 is easily computed, and turns out to also be polynomial in these variables (see (S83) in SM). Using that covariant derivatives on a submanifold are computed by projecting ordinary derivatives in the flat embedding space onto the submanifold, we argue that this polynomial nature is preserved under the operation of taking covariant derivatives, and conclude that I ( E r , m ( a ) ) \mathcal{I}(E_r,m^{(a)}) I ( E r , m ( a ) ) is a polynomial in its arguments. Upon integrating, it follows from Eq. (28) that ln Z \ln Z ln Z takes the analytic form Eq. (3) .
Next, we act on Eq. (28) with the Z κ + 1 \mathbb{Z}_{\kappa+1} Z κ + 1 symmetrization operator (see (7)). E r E_r E r and m i m_i m i are unchanged by permutations, and Ω a ∘ V = ( − 1 ) κ a V \Omega^a\circ\mathcal{V}=(-1)^{\kappa a}\mathcal{V} Ω a ∘ V = ( − 1 ) κa V . It follows that Ω a \Omega^a Ω a effectively acts only on the integration range D 0 D_0 D 0 , turning it into the new simplex D a D_a D a constructed out of the vectors
( p a b ) j = b a 2 j − b b 2 j b a 2 − b b 2 , ( b = 0 … κ , b ≠ a ) , (30) (p_{ab})_j=\frac{b_a^{2j}-b_b^{2j}}{b_a^2-b_b^2},\qquad(b=0\ldots\kappa,\ b\ne a), \tag*{(30)} ( p ab ) j = b a 2 − b b 2 b a 2 j − b b 2 j , ( b = 0 … κ , b = a ) , (30)
with orientation and signs described around Eq. (194) in SM.
The ( κ + 1 ) (\kappa+1) ( κ + 1 ) distinct simplices above each share exactly one corner with every other simplex. The topological manner in which these simplices are sewn together can be visualized as follows. Consider the intersection of a codimension one plane with the unit cube in a Euclidean R κ + 1 \mathbb{R}^{\kappa+1} R κ + 1 space defined by
Δ ( 2 , κ + 1 ) = { ( t 0 , … , t κ ) : 0 ≤ t a ≤ 1 , ∑ a t a = 2 } . (31) \Delta(2,\kappa+1)=\left\{(t_0,\ldots,t_\kappa):0\le t_a\le1,\ \sum_a t_a=2\right\}. \tag*{(31)} Δ ( 2 , κ + 1 ) = { ( t 0 , … , t κ ) : 0 ≤ t a ≤ 1 , a ∑ t a = 2 } . (31)
(see Figure 3 in SM for a visualization when κ = 2 \kappa=2 κ = 2 ). For κ ≥ 3 \kappa\ge3 κ ≥ 3 , this κ \kappa κ dimensional solid shape has 2 ( κ + 1 ) 2(\kappa+1) 2 ( κ + 1 ) distinct boundary surfaces. We identify the ( κ + 1 ) (\kappa+1) ( κ + 1 ) surfaces t a = 1 t_a=1 t a = 1 (a = 0 … κ a=0\ldots\kappa a = 0 … κ ) with our integration simplices D a \mathcal{D}_a D a . We identify the remaining ( κ + 1 ) (\kappa+1) ( κ + 1 ) surfaces t a = 0 t_a=0 t a = 0 (a = 0 … κ a=0\ldots\kappa a = 0 … κ ) with H a \mathcal{H}_a H a , the gaps between integration regions. In the case d = 6 d=6 d = 6 , the relative arrangement of the D a \mathcal{D}_a D a and the holes H a \mathcal{H}_a H a is depicted in Figure 1 .
Figure 1. The d = 6 d=6 d = 6 polytope Δ ( 2 , 4 ) \Delta(2,4) Δ ( 2 , 4 ) . Its six corners are labeled by the six unordered pairs ( a , b ) (a,b) ( a , b ) . The four blue shaded triangular faces constitute the domain of integration, while the other four triangular faces are the ‘holes’ H a \mathcal{H}_a H a .
Figure 3. The polytope Δ ( 2 , κ + 1 ) \Delta(2,\kappa+1) Δ ( 2 , κ + 1 ) for κ = 2 \kappa=2 κ = 2 . Panel (a) shows it as the triangle cut out of the unit cube by the plane ∑ a t a = 2 \sum_a t_a=2 ∑ a t a = 2 ; panel (b) shows the same triangle flat. The blue edges are the faces t a = 1 t_a=1 t a = 1 , which map to the integration regions D a \mathcal{D}_a D a . The red vertices are the faces t a = 0 t_a=0 t a = 0 , which map to the boundary regions H a \mathcal{H}_a H a and here degenerate to points. For κ = 2 \kappa=2 κ = 2 the three D a \mathcal{D}_a D a form a closed contour.
As I ( E r , m ( a ) ) \mathcal{I}(E_r,m^{(a)}) I ( E r , m ( a ) ) is polynomial in m ( a ) m^{(a)} m ( a ) , it follows from Stokes’ theorem and the exactness of the polynomial top form Υ \Upsilon Υ , that the integral of Υ \Upsilon Υ over the closed oriented surface consisting of all D a \mathcal{D}_a D a plus H a \mathcal{H}_a H a vanishes. However, we demonstrate around (S157) of SM that in our physical set up, the ‘holes’ H a \mathcal{H}_a H a can be chosen to lie in a ( κ − 2 ) (\kappa-2) ( κ − 2 ) dimensional hyperplane, and so are of one lower dimension than the integration regions D a \mathcal{D}_a D a . As a consequence, the integral over each of the H a \mathcal{H}_a H a vanishes, so the same is true of the sum of integrals over appropriately oriented D a \mathcal{D}_a D a , implying Eq. (6) .
Checks
Exact verification from the Kerr-AdS2 κ + 1 _{2\kappa+1} 2 κ + 1 black hole
Consider Kerr–AdS in ( 2 κ + 1 ) (2\kappa+1) ( 2 κ + 1 ) bulk dimension with horizon radius r + r_+ r + and independent rotation parameters a i a_i a i . We choose units so that the AdS radius is unity. The thermodynamics of Kerr–AdS black holes was worked out in [8 , 9 ] . In d = 2 κ d=2\kappa d = 2 κ , we define the black hole variables ( q 0 , q 1 , ⋯ , q κ ) (q_0,q_1,\cdots,q_\kappa) ( q 0 , q 1 , ⋯ , q κ ) such that
q 0 : = 1 r + , q i : = a i r + , for i = 1 , … , κ . (32) q_0:=\frac{1}{r_+},\qquad q_i:=\frac{a_i}{r_+},\qquad\text{for }i=1,\ldots,\kappa. \tag*{(32)} q 0 := r + 1 , q i := r + a i , for i = 1 , … , κ . (32)
The black hole thermodynamic potentials ( b 0 , b 1 , ⋯ , b κ ) (b_0,b_1,\cdots,b_\kappa) ( b 0 , b 1 , ⋯ , b κ ) (defined in Eq. (6)) turn out to be given in terms of q i q_i q i by
b i = 2 π q i ∏ j = 0 j ≠ i κ ( 1 + q j 2 ) Ξ , for i = 0 , 1 , … , κ (33) b_i=\frac{2\pi q_i\prod_{\substack{j=0\\j\ne i}}^\kappa(1+q_j^2)}{\Xi},\qquad\text{for }i=0,1,\ldots,\kappa \tag*{(33)} b i = Ξ 2 π q i ∏ j = 0 j = i κ ( 1 + q j 2 ) , for i = 0 , 1 , … , κ (33)
where Ξ \Xi Ξ is given by
Ξ : = ∑ i = 0 κ + 1 ( κ − i ) E i ( q 0 2 , … , q κ 2 ) . (34) \Xi:=\sum_{i=0}^{\kappa+1}(\kappa-i)E_i(q_0^2,\ldots,q_\kappa^2). \tag*{(34)} Ξ := i = 0 ∑ κ + 1 ( κ − i ) E i ( q 0 2 , … , q κ 2 ) . (34)
Here E i E_i E i ’s are defined in Eq. (38) . The Kerr-AdS2 κ + 1 _{2\kappa+1} 2 κ + 1 black hole partition function equals
ln Z B H = − I 2 κ + 1 t h = β π κ − 1 8 ( κ − 1 ) ! G 2 κ + 1 ( 1 − q 0 2 ) ∏ i = 1 κ 1 + q i 2 q 0 2 − q i 2 . (35) \ln Z_{\mathrm{BH}}=-I^{\mathrm{th}}_{2\kappa+1}=\frac{\beta\pi^{\kappa-1}}{8(\kappa-1)!G_{2\kappa+1}}(1-q_0^2)\prod_{i=1}^{\kappa}\frac{1+q_i^2}{q_0^2-q_i^2}. \tag*{(35)} ln Z BH = − I 2 κ + 1 th = 8 ( κ − 1 )! G 2 κ + 1 β π κ − 1 ( 1 − q 0 2 ) i = 1 ∏ κ q 0 2 − q i 2 1 + q i 2 . (35)
Now, consider a Z κ + 1 \mathbb{Z}_{\kappa+1} Z κ + 1 transformation that permutes ( q 0 , q 1 , ⋯ , q κ ) (q_0,q_1,\cdots,q_\kappa) ( q 0 , q 1 , ⋯ , q κ ) as (compare Eq. (6))
Ω b h : ( q 0 , q 1 , … , q κ ) → ( q 1 , … , q κ , q 0 ) . (36) \Omega_{\mathrm{bh}}:(q_0,q_1,\ldots,q_\kappa)\to(q_1,\ldots,q_\kappa,q_0). \tag*{(36)} Ω bh : ( q 0 , q 1 , … , q κ ) → ( q 1 , … , q κ , q 0 ) . (36)
It follows immediately from Eq. (33) and Eq. (34) (which is Z κ + 1 \mathbb{Z}_{\kappa+1} Z κ + 1 invariant) that Eq. (36) induces the action Eq. (6) on ( b 0 , b 1 , ⋯ , b κ ) (b_0,b_1,\cdots,b_\kappa) ( b 0 , b 1 , ⋯ , b κ ) so that the Z κ + 1 \mathbb{Z}_{\kappa+1} Z κ + 1 generator Ω b h \Omega_{\mathrm{bh}} Ω bh reproduces the action of Ω \Omega Ω .
Using Eq. (36) we have checked (see around (S165) in SM) that
( 1 + Ω + ⋯ + Ω κ ) ∘ [ ln Z B H β ] = ( − 1 ) κ π κ − 1 4 ( κ − 1 ) ! G 2 κ + 1 = ( − 1 ) κ κ ! a 2 κ (37) \begin{aligned}
\left(1+\Omega+\cdots+\Omega^\kappa\right)\circ\left[\frac{\ln Z_{\mathrm{BH}}}{\beta}\right]=(-1)^\kappa\frac{\pi^{\kappa-1}}{4(\kappa-1)!G_{2\kappa+1}} \\
&=(-1)^\kappa\kappa!a_{2\kappa} \tag*{(37)}
\end{aligned} ( 1 + Ω + ⋯ + Ω κ ) ∘ [ β ln Z BH ] = ( − 1 ) κ 4 ( κ − 1 )! G 2 κ + 1 π κ − 1 = ( − 1 ) κ κ ! a 2 κ (37)
in perfect agreement18 with our general prediction Eq. (7) . Eq. (37) holds as an exact (non-perturbative) identity, and is true at all values of the parameters.
Direct checks at low orders in the small x i x_i x i expansion
While this paper has focused on the study of ln Z \ln Z ln Z in the high temperature expansion, it was argued in [7 ] (see also [10 , 11 , 12 , 13 ] ) that ln Z \ln Z ln Z also admits a closely related second ‘semi-universal’ small x i x_i x i expansion. Order-by-order in this expansion, constraints on ln Z \ln Z ln Z take the form of differential equations on temperature dependent coefficient functions [6 ] . In SM (see around (S18)) we have used the methods of [6 ] to work out the explicit form of the constraints on ln Z r o t β \frac{\ln Z^{\mathrm{rot}}}{\beta} β l n Z rot up to seventh subleading order in small x i x_i x i , in d = 4 d=4 d = 4 . We have then independently reevaluated these constraints, by inserting the small x i x_i x i semi-universal expansion (see Eq. (10) of [6 ] ) into Eq. (6) , Taylor expanding up to the same order in x i x_i x i , and equating coefficients. The two different methods yield identical constraint differential equations. In particular, at lowest nontrivial order in x i x_i x i , both methods yield the single constraint Eq. (76) in SM, in perfect agreement with Eq. (15) of [6 ] at a = 0 a=0 a = 0 .
Discussion
The authors of [6 ] had predicted the existence of an infinite tower of constraints on coefficients of the high temperature expansion, but had no expectation for the precise form of these equations. In this paper we have demonstrated that this entire tower of relations is equivalent to the single, beautiful constraint equation, Eq. (6) .
The order-by-order expansion of this equation in β 2 \beta^2 β 2 yields the simple constraints on polynomial coefficients Eq. (10) .
It would be good to understand the precise conditions on CFTs that guarantee that ln Z \ln Z ln Z is accurately described by a local thermal effective action as assumed in this paper (see [6 , 7 ] for relevant discussion). It would also be useful to generalize our analysis to CP violating theories in dimensions d = 6 , 10 , … d = 6, 10, \ldots d = 6 , 10 , … and to other scenarios [14 , 15 , 16 , 17 , 18 , 19 , 20 ] where thermal EFT has been useful.
Our striking central equation Eq. (6) , which asserts a relationship between thermodynamics in the time direction and in the rotation planes, calls for a direct physical interpretation, perhaps along the lines of Appendix C. However, we emphasize that Eq. (6) has only been derived order-by-order in the high temperature expansion (i.e. in an expansion around ( b 0 , b 1 , … , b κ ) = ( 0 , 0 , … , 0 ) (b_0,b_1,\ldots,b_\kappa)=(0,0,\ldots,0) ( b 0 , b 1 , … , b κ ) = ( 0 , 0 , … , 0 ) ). Since ln Z \ln Z ln Z in Eq. (1) converges only when ∣ Re ( b i ) ∣ < b 0 ∀ i ≠ 0 |\operatorname{Re}(b_i)|<b_0\ \forall i\ne0 ∣ Re ( b i ) ∣ < b 0 ∀ i = 0 (see e.g. [7 , 21 , 22 , 23 , 24 ] ), and as Ω \Omega Ω maps allowed (convergent) values of b i b_i b i to disallowed (divergent) b i b_i b i (see Eq. (6)), any non-perturbative generalization of Eq. (6) would seem to require an analytic continuation of ln Z \ln Z ln Z to divergent values. It is not clear whether such a continuation is actually meaningful (see e.g. [25 , 26 , 27 , 28 ] for relevant discussion).
Relatedly, it was explained in [29 ] that all ‘bulk’ terms (see [29 ] for terminology) in the all-orders expansion of ln Z \ln Z ln Z around the rational point ( b 0 , b 1 … b κ ) = ( 0 , 2 π i r 1 s 1 , 2 π i r 2 s 2 , … , 2 π i r κ s κ ) (b_0,b_1\ldots b_\kappa)=\left(0,\frac{2\pi i r_1}{s_1},\frac{2\pi i r_2}{s_2},\ldots,\frac{2\pi i r_\kappa}{s_\kappa}\right) ( b 0 , b 1 … b κ ) = ( 0 , s 1 2 π i r 1 , s 2 2 π i r 2 , … , s κ 2 π i r κ ) are formally given by 1 S \frac{1}{S} S 1 times the high temperature partition function of this paper, evaluated as a function of S δ b i S\delta b_i S δ b i . Here S S S is the LCM of s 1 , s 2 , … , s κ s_1,s_2,\ldots,s_\kappa s 1 , s 2 , … , s κ , and δ b i \delta b_i δ b i are the small deviations of b i b_i b i away from this rational point. Thus the analysis of this paper determines not just the all-orders expansion of ln Z \ln Z ln Z in the high temperature limit, but also a large part of the expansion about each of the singular rational points above. One may wonder whether the nonperturbative partition function can be reconstructed from a suitably defined sum over these ‘saddle points’; a proposal with echoes of modular invariance (see [30 ] for a potentially related study of free theories).
Finally, it is possible that an analysis similar to that of [6 ] and the current paper can also be carried out for the superconformal indices [31 , 32 ] in the so-called Cardy limit (see e.g. [33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ] ). Such a study would require the generalization to partition functions with additional conserved R R R charges (and possibly critical chemical potentials [23 , 48 ] ).
Acknowledgments
We thank E. D’Hoker, T. Dumitrescu, H. T. Lam, O. Parrikar, P. Rath, V. Schomerus, S. Trivedi, and Y. Wang for very useful discussions. We would also like to thank K. Bajaj, J. Choi, K. Jensen, Z. Komargodski, A. Miscioscia, C. Patel, F. Popov, S. Van Leeuwen, and S. Wadia for comments on a preliminary version of this manuscript. N.B. is supported by the U.S. Department of Energy, Office of Science, under grant Contract Number DE-SC0026324. The work of A.A., H.A., A.G., V.K., S.M., J.M., S.P., A.R. and P.R. was supported by the Department of Atomic Energy, Government of India, under Project Identification Number RTI-4012 and the Infosys Endowment for the study of the Quantum Structure of Spacetime. A.A., H.A., A.G., V.K., S.M., J.M., S.P., A.R. and P.R. would also like to acknowledge their debt to the people of India for their steady support of the study of basic science.
AI Disclosure Statement
The formula in the last line of Eq. (3) was developed in discussions with Claude Fable 5.1; the study of κ ≥ 3 \kappa\ge3 κ ≥ 3 (the material between Eq. (121) and Eq. (216) in SM) was developed in discussions with ChatGPT Astra 6.1 and independently with Claude Fable 5.1; and the material presented between Eq. (80) and Eq. (93) in SM were developed in discussions with ChatGPT Sol 6.1. In addition, the authors used Claude Opus 5.5 to assist with checks of all calculations and preparation of the figures. Every part of this manuscript (including subsections whose material was developed in discussion with AI tools) is written entirely by the authors. The authors take full responsibility for the scientific content of the paper.
References
Appendix A: Constraining polynomials
Every symmetric polynomial of ( y 0 , y 1 , ⋯ , y κ ) (y_0,y_1,\cdots,y_\kappa) ( y 0 , y 1 , ⋯ , y κ ) can famously be recast as a polynomial of the free generators
E 0 ( y 0 , y 1 , ⋯ , y κ ) : = 1 , E_0(y_0,y_1,\cdots,y_\kappa):=1, E 0 ( y 0 , y 1 , ⋯ , y κ ) := 1 ,
E r ( y 0 , y 1 , ⋯ , y κ ) : = ∑ 0 ≤ i 1 < ⋯ < i r ≤ κ y i 1 ⋯ y i r , for r = 1 , ⋯ , κ + 1. (38) E_r(y_0,y_1,\cdots,y_\kappa):=\sum_{0\leq i_1<\cdots<i_r\leq\kappa}y_{i_1}\cdots y_{i_r},\quad\text{for }r=1,\cdots,\kappa+1. \tag*{(38)} E r ( y 0 , y 1 , ⋯ , y κ ) := 0 ≤ i 1 < ⋯ < i r ≤ κ ∑ y i 1 ⋯ y i r , for r = 1 , ⋯ , κ + 1. (38)
Note that each of ( y 0 , y 1 , ⋯ , y κ ) (y_0,y_1,\cdots,y_\kappa) ( y 0 , y 1 , ⋯ , y κ ) clearly obeys the equation
w κ + 1 − E 1 w κ + ⋯ + ( − 1 ) r E r w κ + 1 − r + ⋯ + ( − 1 ) κ + 1 E κ + 1 = 0. (39) w^{\kappa+1}-E_1w^\kappa+\cdots+(-1)^rE_rw^{\kappa+1-r}+\cdots+(-1)^{\kappa+1}E_{\kappa+1}=0. \tag*{(39)} w κ + 1 − E 1 w κ + ⋯ + ( − 1 ) r E r w κ + 1 − r + ⋯ + ( − 1 ) κ + 1 E κ + 1 = 0. (39)
Now consider a polynomial of the above variables that is completely symmetric in y 1 ⋯ y κ y_1\cdots y_\kappa y 1 ⋯ y κ , but has no particular symmetry under interchanges involving y 0 y_0 y 0 . Any such polynomial can be written as a polynomial in E 1 , E 2 , ⋯ , E κ + 1 E_1,E_2,\cdots,E_{\kappa+1} E 1 , E 2 , ⋯ , E κ + 1 and y 0 y_0 y 0 . As y 0 y_0 y 0 obeys Eq. (39) , however, powers of y 0 y_0 y 0 that are ≥ κ + 1 \geq\kappa+1 ≥ κ + 1 can all be traded for lower powers of y 0 y_0 y 0 multiplying arbitrary polynomials of E r E_r E r . It thus follows that the most general polynomial symmetric in y 1 ⋯ y κ y_1\cdots y_\kappa y 1 ⋯ y κ can be written in the form Eq. (9) , with y i = b i 2 y_i=b_i^2 y i = b i 2 .
In SM (see around (S51)) we insert (10) into Eq. (3) , and then insert this expansion into Eq. (6) , and equate powers of β 2 \beta^2 β 2 . While this yields no constraints on the polynomials I q ( 0 ) , I q ( 1 ) , … , I q ( κ − 1 ) I_q^{(0)},I_q^{(1)},\ldots,I_q^{(\kappa-1)} I q ( 0 ) , I q ( 1 ) , … , I q ( κ − 1 ) , it forces
I q ( κ ) = 0 , ∀ q ≥ κ . (40) I_q^{(\kappa)}=0,\quad\forall q\geq\kappa. \tag*{(40)} I q ( κ ) = 0 , ∀ q ≥ κ . (40)
Eq. (40) expresses a simple universal constraint on the coefficient functions of the high temperature expansion.
Appendix B: Simplification at cyclotomic points
Throughout this Appendix we work at the special values
( ω 1 2 , ω 2 2 … ω κ 2 ) = ( e 2 π i κ + 1 , e 4 π i κ + 1 , … , e 2 π κ i κ + 1 ) (41) (\omega_1^2,\omega_2^2\ldots\omega_\kappa^2)=\left(e^{\frac{2\pi i}{\kappa+1}},e^{\frac{4\pi i}{\kappa+1}},\ldots,e^{\frac{2\pi\kappa i}{\kappa+1}}\right) \tag*{(41)} ( ω 1 2 , ω 2 2 … ω κ 2 ) = ( e κ + 1 2 π i , e κ + 1 4 π i , … , e κ + 1 2 π κi ) (41)
which implies
( b 0 2 , b 1 2 , … b κ 2 ) = β 2 ( 1 , e 2 π i κ + 1 , … , e 2 π κ i κ + 1 ) (b_0^2,b_1^2,\ldots b_\kappa^2)=\beta^2\left(1,e^{\frac{2\pi i}{\kappa+1}},\ldots,e^{\frac{2\pi\kappa i}{\kappa+1}}\right) ( b 0 2 , b 1 2 , … b κ 2 ) = β 2 ( 1 , e κ + 1 2 π i , … , e κ + 1 2 π κi )
⟹ Ω ∘ ( b 0 2 , b 1 2 , … , b κ 2 ) = β 2 ( e 2 π i κ + 1 , e 4 π i κ + 1 , … , e 2 π κ i κ + 1 , 1 ) = e 2 π i κ + 1 ( b 0 2 , b 1 2 , b 2 2 , … , b κ 2 ) . (42) \Longrightarrow\Omega\circ(b_0^2,b_1^2,\ldots,b_\kappa^2)=\beta^2\left(e^{\frac{2\pi i}{\kappa+1}},e^{\frac{4\pi i}{\kappa+1}},\ldots,e^{\frac{2\pi\kappa i}{\kappa+1}},1\right)
=e^{\frac{2\pi i}{\kappa+1}}(b_0^2,b_1^2,b_2^2,\ldots,b_\kappa^2). \tag*{(42)} ⟹ Ω ∘ ( b 0 2 , b 1 2 , … , b κ 2 ) = β 2 ( e κ + 1 2 π i , e κ + 1 4 π i , … , e κ + 1 2 π κi , 1 ) = e κ + 1 2 π i ( b 0 2 , b 1 2 , b 2 2 , … , b κ 2 ) . (42)
Consider any degree h h h homogeneous function f f f of the b μ 2 b_\mu^2 b μ 2 , μ = 0 ⋯ κ \mu=0\cdots\kappa μ = 0 ⋯ κ , where h h h is an integer. It follows immediately from Eq. (42) that the action of the cyclic symmetrization operator
S = 1 + Ω + Ω 2 + ⋯ + Ω κ κ + 1 (43) \mathcal{S}=\frac{1+\Omega+\Omega^2+\cdots+\Omega^\kappa}{\kappa+1} \tag*{(43)} S = κ + 1 1 + Ω + Ω 2 + ⋯ + Ω κ (43)
on f f f yields f f f when h h h is an integral multiple of κ + 1 \kappa+1 κ + 1 , but equals zero otherwise. As the homogeneity of ln Z β \frac{\ln Z}{\beta} β l n Z in b μ 2 b_\mu^2 b μ 2 is the same as its homogeneity in β 2 \beta^2 β 2 , it follows that the action of S \mathcal{S} S on this function (at the special values of ω i 2 \omega_i^2 ω i 2 ) is simply a projector onto the terms in its power series expansion proportional to ( β 2 ) q ( κ + 1 ) (\beta^2)^{q(\kappa+1)} ( β 2 ) q ( κ + 1 ) for all integer q q q . At these special values of ω i 2 \omega_i^2 ω i 2 it thus follows that the LHS of (8) equals
( κ + 1 ) S ∘ ( ln Z β ) = ( κ + 1 ) ∑ q = 0 ∞ ( β 2 ) ( κ + 1 ) q [ ln Z β ] ( β 2 ) ( κ + 1 ) q , (44) (\kappa+1)\mathcal{S}\circ\left(\frac{\ln Z}{\beta}\right)
=(\kappa+1)\sum_{q=0}^{\infty}(\beta^2)^{(\kappa+1)q}\left[\frac{\ln Z}{\beta}\right]_{(\beta^2)^{(\kappa+1)q}}, \tag*{(44)} ( κ + 1 ) S ∘ ( β ln Z ) = ( κ + 1 ) q = 0 ∑ ∞ ( β 2 ) ( κ + 1 ) q [ β ln Z ] ( β 2 ) ( κ + 1 ) q , (44)
where ∣ ∣ β n \left.\vphantom{\big|}\right|_{\beta^n} β n denotes the coefficient of β n \beta^n β n . Inserting Eq. (44) into (8) and comparing powers of β 2 \beta^2 β 2 we conclude that
( κ + 1 ) × [ ln Z β ] ( β 2 ) ( κ + 1 ) q = ( − 1 ) κ κ ! a 2 κ δ q , 0 , ∀ q ∈ Z ≥ 0 (45) (\kappa+1)\times\left[\frac{\ln Z}{\beta}\right]_{(\beta^2)^{(\kappa+1)q}}=(-1)^\kappa\kappa!a_{2\kappa}\delta_{q,0},\quad\forall q\in\mathbb{Z}_{\geq0} \tag*{(45)} ( κ + 1 ) × [ β ln Z ] ( β 2 ) ( κ + 1 ) q = ( − 1 ) κ κ ! a 2 κ δ q , 0 , ∀ q ∈ Z ≥ 0 (45)
in perfect agreement with Eq. (6) and Eq. (21) of [6 ] .
In this Appendix, we construct three large conformal maps that cycle through S 3 × R S^3\times R S 3 × R , A d S 3 × S 1 AdS_3\times S^1 A d S 3 × S 1 , and a second copy of A d S 3 × S 1 AdS_3\times S^1 A d S 3 × S 1 (see (24) ) closing in to the Z 3 \mathbb{Z}_3 Z 3 action on the b i b_i b i .
Consider the metric g μ ν g_{\mu\nu} g μν
d s 2 = d τ 2 + d θ 2 + sin 2 θ d ϕ 1 2 + cos 2 θ d ϕ 2 2 = d τ 2 + d l 2 4 ( 1 − l ) l + l d ϕ 1 2 + ( 1 − l ) d ϕ 2 2 , (46) \begin{aligned}
ds^2=d\tau^2+d\theta^2+\sin^2\theta\,d\phi_1^2+\cos^2\theta\,d\phi_2^2 \\
&=d\tau^2+\frac{dl^2}{4(1-l)l}+l\,d\phi_1^2+(1-l)d\phi_2^2, \tag*{(46)}
\end{aligned} d s 2 = d τ 2 + d θ 2 + sin 2 θ d ϕ 1 2 + cos 2 θ d ϕ 2 2 = d τ 2 + 4 ( 1 − l ) l d l 2 + l d ϕ 1 2 + ( 1 − l ) d ϕ 2 2 , (46)
where l = sin 2 θ l=\sin^2\theta l = sin 2 θ , l ∈ ( 0 , 1 ) l\in(0,1) l ∈ ( 0 , 1 ) .
Map to A d S 3 × S 1 AdS_3\times S^1 A d S 3 × S 1
Pulling out an overall factor of l l l , we conclude (C1) ∼ \sim ∼
d s 2 = d τ 2 l + d ϕ 1 2 + 1 − l l d ϕ 2 2 + d l 2 4 l 2 ( 1 − l ) (47) ds^2=\frac{d\tau^2}{l}+d\phi_1^2+\frac{1-l}{l}d\phi_2^2+\frac{dl^2}{4l^2(1-l)} \tag*{(47)} d s 2 = l d τ 2 + d ϕ 1 2 + l 1 − l d ϕ 2 2 + 4 l 2 ( 1 − l ) d l 2 (47)
where ∼ \sim ∼ denotes Weyl equivalence. Note that ϕ 1 \phi_1 ϕ 1 is non-contractible in Eq. (47) . Changing coordinates,
l = 1 1 − l ~ , l ~ ∈ ( − ∞ , 0 ) , (48) l=\frac{1}{1-\tilde l},\quad\tilde l\in(-\infty,0), \tag*{(48)} l = 1 − l ~ 1 , l ~ ∈ ( − ∞ , 0 ) , (48)
d s 2 = ( 1 − l ~ ) d τ 2 + d ϕ 1 2 − l ~ d ϕ 2 2 − d l ~ 2 4 l ~ ( 1 − l ~ ) . ds^2=(1-\tilde l)d\tau^2+d\phi_1^2-\tilde l\,d\phi_2^2-\frac{d\tilde l^2}{4\tilde l(1-\tilde l)}. d s 2 = ( 1 − l ~ ) d τ 2 + d ϕ 1 2 − l ~ d ϕ 2 2 − 4 l ~ ( 1 − l ~ ) d l ~ 2 .
The further redefinition l ~ = − sinh 2 ρ \tilde l=-\sinh^2\rho l ~ = − sinh 2 ρ , ρ ∈ ( 0 , ∞ ) \rho\in(0,\infty) ρ ∈ ( 0 , ∞ ) gives
d s 2 = d ϕ 1 2 + d ρ 2 + cosh 2 ρ d τ 2 + sinh 2 ρ d ϕ 2 2 , (49) ds^2=d\phi_1^2+d\rho^2+\cosh^2\rho\,d\tau^2+\sinh^2\rho\,d\phi_2^2, \tag*{(49)} d s 2 = d ϕ 1 2 + d ρ 2 + cosh 2 ρ d τ 2 + sinh 2 ρ d ϕ 2 2 , (49)
the metric of (Euclidean) A d S 3 × S 1 AdS_3\times S^1 A d S 3 × S 1 . The codimension one boundary ρ → ∞ \rho\to\infty ρ → ∞ of the A d S 3 AdS_3 A d S 3 metric is a ‘blow up’ of the codimension two surface l = 0 l=0 l = 0 on which the ϕ 1 \phi_1 ϕ 1 circle shrinks in the original metric Eq. (46) .
The CFT path integral on S 3 × R S^3 \times R S 3 × R is thus Weyl equivalent to the path integral on H 3 × S 1 H_3 \times S^1 H 3 × S 1 . The identification Eq. (14) carries over to the H 3 × S 1 H_3 \times S^1 H 3 × S 1 path integral, which thus computes
Tr H 3 × S 1 e − β H + β ω 2 J + β ω 1 Q (50) \operatorname{Tr}_{H_3 \times S^1} e^{-\beta H+\beta\omega_2 J+\beta\omega_1 Q} \tag*{(50)} Tr H 3 × S 1 e − β H + β ω 2 J + β ω 1 Q (50)
where H H H is the usual global Hamiltonian of A d S 3 AdS_3 A d S 3 , J J J generates angular momentum (translation on the boundary S 1 S^1 S 1 ) of A d S 3 AdS_3 A d S 3 and Q Q Q is the charge on the non-contractible S 1 S^1 S 1 parametrized by the angle ϕ 1 \phi_1 ϕ 1 . We thus conclude that the trace Eq. (50) is identical to the S 3 × S 1 S^3 \times S^1 S 3 × S 1 trace studied in this paper. We emphasize that the equality Eq. (50) is a nonperturbative statement; the partition function on S 3 × R S^3 \times R S 3 × R and on A d S 3 × S 1 AdS_3 \times S^1 A d S 3 × S 1 , with the identification Eq. (14) , are literally the same function. In SM, we check this equivalence for a free conformally coupled scalar.
Analytic continuation to S 3 × R S^3 \times R S 3 × R
The complex variable change
( τ , ϕ 1 , ϕ 2 ) = ( i ϕ ~ 2 , − i τ ~ , ϕ ~ 1 ) (51) (\tau,\phi_1,\phi_2) = (i\widetilde{\phi}_2,-i\widetilde{\tau},\widetilde{\phi}_1) \tag*{(51)} ( τ , ϕ 1 , ϕ 2 ) = ( i ϕ 2 , − i τ , ϕ 1 ) (51)
turns the A d S 3 × S 1 AdS_3 \times S^1 A d S 3 × S 1 metric in (C4) to
d s 2 = − ( d τ ~ 2 + d l ~ 2 4 l ~ ( 1 − l ~ ) + l ~ d ϕ ~ 1 2 + ( 1 − l ~ ) d ϕ ~ 2 2 ) . (52) ds^2=-\left(d\widetilde{\tau}^2+\frac{d\widetilde{l}^2}{4\widetilde{l}(1-\widetilde{l})}+\widetilde{l}\,d\widetilde{\phi}_1^2+(1-\widetilde{l})d\widetilde{\phi}_2^2\right). \tag*{(52)} d s 2 = − ( d τ 2 + 4 l ( 1 − l ) d l 2 + l d ϕ 1 2 + ( 1 − l ) d ϕ 2 2 ) . (52)
Up to a Weyl transformation that removes the overall minus sign, Eq. (52) has the same form in tilde coordinates, as the metric Eq. (46) had in the old coordinates, and so yields S 3 × R S^3 \times R S 3 × R . We conclude that the analytic continuation of l ~ \widetilde{l} l from the ‘physical range’ listed in Eq. (48) to the ‘unphysical’ range l ~ ∈ ( 0 , 1 ) \widetilde{l} \in(0,1) l ∈ ( 0 , 1 ) turns A d S 3 × S 1 AdS_3 \times S^1 A d S 3 × S 1 into a second S 3 × R S^3 \times R S 3 × R spacetime.
Since
( ∂ τ , − i ∂ ϕ 1 , − i ∂ ϕ 2 ) = ( − i ∂ ϕ ~ 2 , ∂ τ ~ , − i ∂ ϕ ~ 1 ) , (53) (\partial_\tau,-i\partial_{\phi_1},-i\partial_{\phi_2})=(-i\partial_{\widetilde{\phi}_2},\partial_{\widetilde{\tau}},-i\partial_{\widetilde{\phi}_1}), \tag*{(53)} ( ∂ τ , − i ∂ ϕ 1 , − i ∂ ϕ 2 ) = ( − i ∂ ϕ 2 , ∂ τ , − i ∂ ϕ 1 ) , (53)
it follows that
v = b 0 ∂ τ + b 1 ( − i ∂ ϕ 1 ) + b 2 ( − i ∂ ϕ 2 ) = b ~ 0 ∂ τ ~ + b ~ 1 ( − i ∂ ϕ ~ 1 ) + b ~ 2 ( − i ∂ ϕ ~ 2 ) (54) v=b_0\partial_\tau+b_1(-i\partial_{\phi_1})+b_2(-i\partial_{\phi_2})
=\widetilde{b}_0\partial_{\widetilde{\tau}}+\widetilde{b}_1(-i\partial_{\widetilde{\phi}_1})+\widetilde{b}_2(-i\partial_{\widetilde{\phi}_2}) \tag*{(54)} v = b 0 ∂ τ + b 1 ( − i ∂ ϕ 1 ) + b 2 ( − i ∂ ϕ 2 ) = b 0 ∂ τ + b 1 ( − i ∂ ϕ 1 ) + b 2 ( − i ∂ ϕ 2 ) (54)
where ( b ~ 0 , b ~ 1 , b ~ 2 ) = ( b 1 , b 2 , b 0 ) (\widetilde{b}_0,\widetilde{b}_1,\widetilde{b}_2)=(b_1,b_2,b_0) ( b 0 , b 1 , b 2 ) = ( b 1 , b 2 , b 0 ) .
The variable z z z defined in Eq. (15) is related to l l l via
z = ( 1 − l ) b 0 2 b 1 2 − b 1 2 b 2 2 + l b 2 2 b 0 2 b 0 2 − l b 1 2 + ( l − 1 ) b 2 2 , z ~ = ( 1 − l ~ ) b ~ 0 2 b ~ 1 2 − b ~ 1 2 b ~ 2 2 + l ~ b ~ 2 2 b ~ 0 2 b ~ 0 2 − l ~ b ~ 1 2 + ( l ~ − 1 ) b ~ 2 2 . (55) z=\frac{(1-l)b_0^2b_1^2-b_1^2b_2^2+lb_2^2b_0^2}{b_0^2-lb_1^2+(l-1)b_2^2},
\qquad
\widetilde{z}=\frac{(1-\widetilde{l})\widetilde{b}_0^2\widetilde{b}_1^2-\widetilde{b}_1^2\widetilde{b}_2^2+\widetilde{l}\widetilde{b}_2^2\widetilde{b}_0^2}{\widetilde{b}_0^2-\widetilde{l}\widetilde{b}_1^2+(\widetilde{l}-1)\widetilde{b}_2^2}. \tag*{(55)} z = b 0 2 − l b 1 2 + ( l − 1 ) b 2 2 ( 1 − l ) b 0 2 b 1 2 − b 1 2 b 2 2 + l b 2 2 b 0 2 , z = b 0 2 − l b 1 2 + ( l − 1 ) b 2 2 ( 1 − l ) b 0 2 b 1 2 − b 1 2 b 2 2 + l b 2 2 b 0 2 . (55)
Inserting Eq. (48) into Eq. (55) , it is easily verified that z ~ = z \widetilde{z}=z z = z .
Now consider the quantity I \mathcal{I} I evaluated in the original geometry. Following I \mathcal{I} I through the coordinate transforms performed above, and using its Weyl invariance, we find
I b 0 , b 1 , b 2 ( z ) = I b 1 , b 2 , b 0 ( z ) (56) \mathcal{I}_{b_0,b_1,b_2}(z)=\mathcal{I}_{b_1,b_2,b_0}(z) \tag*{(56)} I b 0 , b 1 , b 2 ( z ) = I b 1 , b 2 , b 0 ( z ) (56)
yielding a structural explanation for Eq. (19) .
We can now rerun this analysis with the role of ϕ 1 \phi_1 ϕ 1 and ϕ 2 \phi_2 ϕ 2 exchanged. We pull out the factor ( 1 − l ) (1-l) ( 1 − l ) (rather than l l l ) from Eq. (46) , to obtain a second A d S 3 × S 1 AdS_3 \times S^1 A d S 3 × S 1 . The analogous analytic continuation then produces a third S 3 × R S^3 \times R S 3 × R , explaining the full Z 3 Z_3 Z 3 action.
The workout of this Appendix generalizes in a straightforward manner to d = 2 κ d=2\kappa d = 2 κ for arbitrary κ ≥ 3 \kappa\ge3 κ ≥ 3 .
Appendix D: Counting constraints Eq. (40)
Completely Bose symmetric degree-q q q homogeneous polynomials of ( b 0 2 , b 1 2 … b κ 2 ) (b_0^2,b_1^2\ldots b_\kappa^2) ( b 0 2 , b 1 2 … b κ 2 ) are freely generated by the degree 1 , 2 , … , κ + 1 1,2,\ldots,\kappa+1 1 , 2 , … , κ + 1 generators, E 1 E_1 E 1 , E 2 … E κ + 1 E_2\ldots E_{\kappa+1} E 2 … E κ + 1 (see Eq. (38) ). Such polynomials thus constitute an n q s y m n_q^{\mathrm{sym}} n q sym dimensional vector space where
1 ∏ i = 1 κ + 1 ( 1 − t i ) = ∑ q = 0 ∞ n q s y m t q . (57) \frac{1}{\prod_{i=1}^{\kappa+1}(1-t^i)}=\sum_{q=0}^{\infty}n_q^{\mathrm{sym}}t^q. \tag*{(57)} ∏ i = 1 κ + 1 ( 1 − t i ) 1 = q = 0 ∑ ∞ n q sym t q . (57)
It follows from Eq. (9) that polynomials symmetrical only under permutations of ( b 1 2 , b 2 2 , … , b κ 2 ) (b_1^2,b_2^2,\ldots,b_\kappa^2) ( b 1 2 , b 2 2 , … , b κ 2 ) lie in an n q b n_q^b n q b dimensional vector space, with
∑ i = 0 κ t i ∏ i = 1 κ + 1 ( 1 − t i ) = 1 ( 1 − t ) 2 ∏ i = 2 κ ( 1 − t i ) = ∑ q = 0 ∞ n q b t q (58) \frac{\sum_{i=0}^{\kappa}t^i}{\prod_{i=1}^{\kappa+1}(1-t^i)}=\frac{1}{(1-t)^2\prod_{i=2}^{\kappa}(1-t^i)}=\sum_{q=0}^{\infty}n_q^b t^q \tag*{(58)} ∏ i = 1 κ + 1 ( 1 − t i ) ∑ i = 0 κ t i = ( 1 − t ) 2 ∏ i = 2 κ ( 1 − t i ) 1 = q = 0 ∑ ∞ n q b t q (58)
in agreement with the ‘naive count’, Eq. (C.3) of [6 ] .
Similarly, degree q q q polynomials that take the form Eq. (9) , but with I q ( κ ) = 0 I_q^{(\kappa)}=0 I q ( κ ) = 0 , lie in an n q m n_q^m n q m dimensional space, with
∑ i = 0 κ − 1 t i ∏ i = 1 κ − 1 ( 1 − t i ) = 1 ( 1 − t ) 2 ( 1 − t κ + 1 ) ∏ i = 2 κ − 1 ( 1 − t i ) = ∑ q = 0 ∞ n q m t q (59) \begin{aligned}
\frac{\sum_{i=0}^{\kappa-1}t^i}{\prod_{i=1}^{\kappa-1}(1-t^i)}=\frac{1}{(1-t)^2(1-t^{\kappa+1})\prod_{i=2}^{\kappa-1}(1-t^i)} \\
&=\sum_{q=0}^{\infty}n_q^m t^q \tag*{(59)}
\end{aligned} ∏ i = 1 κ − 1 ( 1 − t i ) ∑ i = 0 κ − 1 t i = ( 1 − t ) 2 ( 1 − t κ + 1 ) ∏ i = 2 κ − 1 ( 1 − t i ) 1 = q = 0 ∑ ∞ n q m t q (59)
in agreement with the local count Eq. C.4 of [6 ] .
By subtracting Eq. (59) from Eq. (58) , we see by comparison with Eq. (5) that the condition that I q ( κ ) = 0 I_q^{(\kappa)}=0 I q ( κ ) = 0 imposes n q b − n q m = d q n_q^b-n_q^m=d_q n q b − n q m = d q constraints on the polynomial T q T_q T q in perfect agreement with the predictions of [6 ] . See around Eq. (120) in SM for an S 3 S_3 S 3 representation take on all these formulae.
Supplemental Material
Computation of the measure factor
In the coordinates Eq. (12) , the measure factor in Eq. (11) equals
d 4 x g 4 ( V 2 ) 2 = cos θ sin θ d ϕ 1 d ϕ 2 d τ d θ β 4 ( 1 − ω 1 2 sin 2 θ − ω 2 2 cos 2 θ ) 2 = 1 2 β 4 d ϕ 1 d ϕ 2 d τ d ( sin 2 θ ) [ 1 − ω 2 2 + sin 2 θ ( ω 2 2 − ω 1 2 ) ] 2 = d ϕ 1 d ϕ 2 d τ 2 β 4 ( ω 1 2 − ω 2 2 ) d ( 1 1 − ω 2 2 + sin 2 θ ( ω 2 2 − ω 1 2 ) ) = d γ 2 d ϕ 1 d ϕ 2 d τ 2 β 4 ( ω 1 2 − ω 2 2 ) = − d z d ϕ 1 d ϕ 2 d τ 2 ( b 1 2 − b 2 2 ) ( b 0 2 − b 1 2 ) ( b 0 2 − b 2 2 ) (60) \frac{d^4x\sqrt{g_4}}{(\mathcal{V}^2)^2}
= \frac{\cos\theta\sin\theta\,d\phi_1d\phi_2d\tau d\theta}{\beta^4(1-\omega_1^2\sin^2\theta-\omega_2^2\cos^2\theta)^2}
= \frac{1}{2\beta^4}\frac{d\phi_1d\phi_2d\tau d(\sin^2\theta)}{[1-\omega_2^2+\sin^2\theta(\omega_2^2-\omega_1^2)]^2}
= \frac{d\phi_1d\phi_2d\tau}{2\beta^4(\omega_1^2-\omega_2^2)}d\left(\frac{1}{1-\omega_2^2+\sin^2\theta(\omega_2^2-\omega_1^2)}\right)
= \frac{d\gamma^2d\phi_1d\phi_2d\tau}{2\beta^4(\omega_1^2-\omega_2^2)}
= -\frac{dzd\phi_1d\phi_2d\tau}{2(b_1^2-b_2^2)(b_0^2-b_1^2)(b_0^2-b_2^2)} \tag*{(60)} ( V 2 ) 2 d 4 x g 4 = β 4 ( 1 − ω 1 2 sin 2 θ − ω 2 2 cos 2 θ ) 2 cos θ sin θ d ϕ 1 d ϕ 2 d τ d θ = 2 β 4 1 [ 1 − ω 2 2 + sin 2 θ ( ω 2 2 − ω 1 2 ) ] 2 d ϕ 1 d ϕ 2 d τ d ( sin 2 θ ) = 2 β 4 ( ω 1 2 − ω 2 2 ) d ϕ 1 d ϕ 2 d τ d ( 1 − ω 2 2 + sin 2 θ ( ω 2 2 − ω 1 2 ) 1 ) = 2 β 4 ( ω 1 2 − ω 2 2 ) d γ 2 d ϕ 1 d ϕ 2 d τ = − 2 ( b 1 2 − b 2 2 ) ( b 0 2 − b 1 2 ) ( b 0 2 − b 2 2 ) d z d ϕ 1 d ϕ 2 d τ (60)
where γ 2 \gamma^2 γ 2 was defined in Eq. (15) and z z z was defined in Eq. (15) . 19 Consequently, Eq. (11) reduces to Eq. (17) .
χ = x 1 ℓ x 2 + ( x 1 − x 2 ) ℓ , ( ℓ = sin 2 θ ) \chi=\frac{x_1\ell}{x_2+(x_1-x_2)\ell},\qquad(\ell=\sin^2\theta) χ = x 2 + ( x 1 − x 2 ) ℓ x 1 ℓ , ( ℓ = sin 2 θ )
d χ = x 1 x 2 ( x 2 + ( x 1 − x 2 ) ℓ ) 2 d ℓ = x 1 x 2 ( x 2 − x 1 ) d γ 2 (61) \begin{aligned}
d\chi=\frac{x_1x_2}{(x_2+(x_1-x_2)\ell)^2}d\ell\\
&=\frac{x_1x_2}{(x_2-x_1)}d\gamma^2 \tag*{(61)}
\end{aligned} d χ = ( x 2 + ( x 1 − x 2 ) ℓ ) 2 x 1 x 2 d ℓ = ( x 2 − x 1 ) x 1 x 2 d γ 2 (61)
so that
γ 2 = ( 1 − χ ) x 1 + x 2 χ x 1 x 2 (62) \gamma^2=\frac{(1-\chi)x_1+x_2\chi}{x_1x_2} \tag*{(62)} γ 2 = x 1 x 2 ( 1 − χ ) x 1 + x 2 χ (62)
Explicit constraints at low orders
In the main text of this paper, we have verified that the expansion of Eq. (6) , at order β 2 q \beta^{2q} β 2 q , yields d q d_q d q constraints (see around Eq. (5) for a definition of d q d_q d q ), in perfect agreement with the constraints derived and counted in [6 ] using a different method. Recall that the constraints derived in [6 ] follow from the fact that I \mathcal{I} I (the integrand of the thermal effective action) admits a power series expansion in the scalars listed in Eq. (18) , up to total derivatives that do not affect the final partition function. Since (as we have demonstrated around Eq. (22) ), Eq. (6) also follows from exactly the same assumptions, it follows immediately that the partition functions built out of such I \mathcal{I} I must be a subset of the space of partition functions that obey Eq. (6) . As the space of partition functions that obey Eq. (6) has exactly the same dimension as the space of partition functions with a local I \mathcal{I} I built out of the components in Eq. (18) , it follows that Eq. (6) imposes no additional constraints on I \mathcal{I} I . Consequently the space of partition functions carved out by the methods of this paper must be identical to the space of partition functions described by the paper [6 ] .
As a sanity check, in this section we provide some direct calculational evidence for the conclusion of the previous paragraph. We work in the simplest dimension d = 4 d=4 d = 4 , and present our evidence in an expansion around the ‘semi-universal’ limit
x 1 , x 2 → 0 , ( x 1 x 2 and β ) fixed (63) x_1,x_2\to0,\qquad\left(\frac{x_1}{x_2}\ \text{and}\ \beta\right)\ \text{fixed} \tag*{(63)} x 1 , x 2 → 0 , ( x 2 x 1 and β ) fixed (63)
(see [6 , 7 ] ), rather than the ‘high temperature’ expansion in small β 2 \beta^2 β 2 , employed in most of the rest of this paper. We make this choice for the following reason. In the high temperature expansion Eq. (3) , the coefficient of β 2 q \beta^{2q} β 2 q is a polynomial of degree q q q in the variables x i x_i x i . As degree q q q polynomials are characterized by a finite number of coefficients, we find only a finite number, d q d_q d q constraints, at any given value of q q q . In the small x i x_i x i ‘semi-universal’ expansion, on the other hand, coefficients of x 1 m x 2 n x_1^mx_2^n x 1 m x 2 n are functions h m , n ( β 2 ) h_{m,n}(\beta^2) h m , n ( β 2 ) . 20 At every order x i q x_i^q x i q , we obtain ⌊ q 2 ⌋ − ⌊ q 3 ⌋ \left\lfloor\frac{q}{2}\right\rfloor-\left\lfloor\frac{q}{3}\right\rfloor ⌊ 2 q ⌋ − ⌊ 3 q ⌋ new functional equations on these constraint functions at order x i q x_i^q x i q (see [6 ] ). 21 Power series expanding each of these differential relations in β 2 \beta^{2} β 2 yields an infinite number of constraints on coefficients. At a practical level, therefore, the small x i x_i x i expansion is much more efficient than the small β 2 \beta^{2} β 2 expansion; working up to order q q q in small x i x_i x i gives each of the high temperature constraints up to order β 2 q \beta^{2q} β 2 q , plus infinitely more.
In order to extract the constraints that follow from Eq. (6) in a small x i x_i x i expansion, we start with the equation Eq. (64)
( 1 + Ω + Ω 2 ) ∘ [ ln Z r o t ( b 0 2 , b 1 2 , b 2 2 ) β ] = 0 (64) \left(1+\Omega+\Omega^{2}\right)\circ\left[\frac{\ln Z^{\mathrm{rot}}\left(b_{0}^{2},b_{1}^{2},b_{2}^{2}\right)}{\beta}\right]=0 \tag*{(64)} ( 1 + Ω + Ω 2 ) ∘ [ β ln Z rot ( b 0 2 , b 1 2 , b 2 2 ) ] = 0 (64)
where the Z 3 \mathbb{Z}_{3} Z 3 generator Ω \Omega Ω , and ( b 0 , b 1 , b 2 ) (b_{0},b_{1},b_{2}) ( b 0 , b 1 , b 2 ) were defined in Eq. (6). It is useful to define the function H ( b 0 2 , b 1 2 , b 2 2 ) H(b_{0}^{2},b_{1}^{2},b_{2}^{2}) H ( b 0 2 , b 1 2 , b 2 2 ) via
ln Z r o t β = − H ( b 0 2 − b 1 2 ) ( b 0 2 − b 2 2 ) . (65) \frac{\ln Z^{\mathrm{rot}}}{\beta}=-\frac{H}{\left(b_{0}^{2}-b_{1}^{2}\right)\left(b_{0}^{2}-b_{2}^{2}\right)}. \tag*{(65)} β ln Z rot = − ( b 0 2 − b 1 2 ) ( b 0 2 − b 2 2 ) H . (65)
( b 1 2 − b 2 2 ) H ( b 0 2 , b 1 2 , b 2 2 ) + ( b 2 2 − b 0 2 ) H ( b 1 2 , b 2 2 , b 0 2 ) + ( b 0 2 − b 1 2 ) H ( b 2 2 , b 0 2 , b 1 2 ) = 0. (66) \left(b_{1}^{2}-b_{2}^{2}\right)H\left(b_{0}^{2},b_{1}^{2},b_{2}^{2}\right)+\left(b_{2}^{2}-b_{0}^{2}\right)H\left(b_{1}^{2},b_{2}^{2},b_{0}^{2}\right)+\left(b_{0}^{2}-b_{1}^{2}\right)H\left(b_{2}^{2},b_{0}^{2},b_{1}^{2}\right)=0. \tag*{(66)} ( b 1 2 − b 2 2 ) H ( b 0 2 , b 1 2 , b 2 2 ) + ( b 2 2 − b 0 2 ) H ( b 1 2 , b 2 2 , b 0 2 ) + ( b 0 2 − b 1 2 ) H ( b 2 2 , b 0 2 , b 1 2 ) = 0. (66)
We now choose to view H H H as a function of ( β 2 , x 1 , x 2 ) (\beta^{2},x_{1},x_{2}) ( β 2 , x 1 , x 2 ) rather than ( b 0 2 , b 1 2 , b 2 2 ) (b_{0}^{2},b_{1}^{2},b_{2}^{2}) ( b 0 2 , b 1 2 , b 2 2 ) . With this presentation, Eq. (66) becomes
( x 2 − x 1 ) H ( β 2 , x 1 , x 2 ) − x 2 H ( β 2 ( 1 − x 1 ) , Ω x 1 , Ω x 2 ) + x 1 H ( β 2 ( 1 − x 2 ) , Ω 2 x 1 , Ω 2 x 2 ) = 0 , (67) (x_{2}-x_{1})H(\beta^{2},x_{1},x_{2})-x_{2}H\left(\beta^{2}(1-x_{1}),\Omega x_{1},\Omega x_{2}\right)+x_{1}H\left(\beta^{2}(1-x_{2}),\Omega^{2}x_{1},\Omega^{2}x_{2}\right)=0, \tag*{(67)} ( x 2 − x 1 ) H ( β 2 , x 1 , x 2 ) − x 2 H ( β 2 ( 1 − x 1 ) , Ω x 1 , Ω x 2 ) + x 1 H ( β 2 ( 1 − x 2 ) , Ω 2 x 1 , Ω 2 x 2 ) = 0 , (67)
where Ω x i \Omega x_i Ω x i denotes the action of Ω \Omega Ω on x i x_i x i , and takes the explicit form
Ω ( x 1 , x 2 ) = ( x 2 − x 1 1 − x 1 , x 1 x 1 − 1 ) , \Omega(x_{1},x_{2})=\left(\frac{x_{2}-x_{1}}{1-x_{1}},\frac{x_{1}}{x_{1}-1}\right), Ω ( x 1 , x 2 ) = ( 1 − x 1 x 2 − x 1 , x 1 − 1 x 1 ) ,
Ω 2 ( x 1 , x 2 ) = ( x 2 x 2 − 1 , x 1 − x 2 1 − x 2 ) . (68) \Omega^{2}(x_{1},x_{2})=\left(\frac{x_{2}}{x_{2}-1},\frac{x_{1}-x_{2}}{1-x_{2}}\right). \tag*{(68)} Ω 2 ( x 1 , x 2 ) = ( x 2 − 1 x 2 , 1 − x 2 x 1 − x 2 ) . (68)
In the second and third terms in Eq. (67) , the first argument β 2 \beta^{2} β 2 has been replaced by β 2 ( 1 − x 1 ) \beta^{2}(1-x_{1}) β 2 ( 1 − x 1 ) and β 2 ( 1 − x 2 ) \beta^{2}(1-x_{2}) β 2 ( 1 − x 2 ) respectively. Consequently the functional relation Eq. (67) is effectively ‘non-local’ in β 2 \beta^{2} β 2 (i.e. the three different terms in that equation are evaluated at different values of β 2 \beta^{2} β 2 ). In the small x i x_i x i expansion, however, the difference in arguments is small, and can be Taylor expanded. For any function F ( β 2 ) F(\beta^{2}) F ( β 2 ) ,
F ( β 2 ( 1 − x i ) ) = ( 1 − x i ) θ F ( β 2 ) , θ = β 2 d d β 2 (69) F\left(\beta^{2}(1-x_i)\right)=(1-x_i)^{\theta}F(\beta^{2}),\qquad\theta=\beta^{2}\frac{d}{d\beta^{2}} \tag*{(69)} F ( β 2 ( 1 − x i ) ) = ( 1 − x i ) θ F ( β 2 ) , θ = β 2 d β 2 d (69)
(one way to verify this equation is to expand F F F in a Taylor series and explicitly work out the RHS). Consequently, Eq. (67) can be rewritten in the form
( x 2 − x 1 ) H ( β 2 , x 1 , x 2 ) − x 2 ( 1 − x 1 ) θ H ( β 2 , Ω x 1 , Ω x 2 ) + x 1 ( 1 − x 2 ) θ H ( β 2 , Ω 2 x 1 , Ω 2 x 2 ) = 0 (70) (x_{2}-x_{1})H(\beta^{2},x_{1},x_{2})-x_{2}(1-x_{1})^{\theta}H(\beta^{2},\Omega x_{1},\Omega x_{2})+x_{1}(1-x_{2})^{\theta}H(\beta^{2},\Omega^{2}x_{1},\Omega^{2}x_{2})=0 \tag*{(70)} ( x 2 − x 1 ) H ( β 2 , x 1 , x 2 ) − x 2 ( 1 − x 1 ) θ H ( β 2 , Ω x 1 , Ω x 2 ) + x 1 ( 1 − x 2 ) θ H ( β 2 , Ω 2 x 1 , Ω 2 x 2 ) = 0 (70)
where
( 1 − x i ) θ = 1 − θ x i + θ ( θ − 1 ) 2 ! x i 2 − θ ( θ − 1 ) ( θ − 2 ) 3 ! x i 3 + … (71) (1-x_i)^{\theta}=1-\theta x_i+\frac{\theta(\theta-1)}{2!}x_i^{2}-\frac{\theta(\theta-1)(\theta-2)}{3!}x_i^{3}+\ldots \tag*{(71)} ( 1 − x i ) θ = 1 − θ x i + 2 ! θ ( θ − 1 ) x i 2 − 3 ! θ ( θ − 1 ) ( θ − 2 ) x i 3 + … (71)
and θ \theta θ is the differential operator given in Eq. (69) .
We now follow [6 ] (See Eq. (11) of [6 ] ) to expand
H = ∑ m , n = 0 ∞ h m , n ( β 2 ) x 1 m x 2 n (72) H=\sum_{m,n=0}^{\infty}h_{m,n}(\beta^{2})x_{1}^{m}x_{2}^{n} \tag*{(72)} H = m , n = 0 ∑ ∞ h m , n ( β 2 ) x 1 m x 2 n (72)
with h m , n ( β 2 ) = h n , m ( β 2 ) h_{m,n}(\beta^2)=h_{n,m}(\beta^2) h m , n ( β 2 ) = h n , m ( β 2 ) . Plugging (72) into (70) , Taylor expanding Ω x i \Omega x_i Ω x i and Ω 2 x i \Omega^2 x_i Ω 2 x i in x i x_i x i , collecting terms and requiring the vanishing of the coefficients of every independent monomial x 1 m x 2 n x_1^m x_2^n x 1 m x 2 n yields several constraint equations. The equation corresponding to the coefficient of monomials with m + n = p m+n=p m + n = p takes the form
∑ a , b > 0 , a ≥ b a + b ≤ p D a , b [ h a , b ( β 2 ) ] = 0. (73) \sum_{\substack{a,b>0,\ a\ge b\\a+b\le p}}D_{a,b}\left[h_{a,b}(\beta^2)\right]=0 . \tag*{(73)} a , b > 0 , a ≥ b a + b ≤ p ∑ D a , b [ h a , b ( β 2 ) ] = 0. (73)
Here D a , b D_{a,b} D a , b is a polynomial in θ \theta θ that is generically of order p − ( a + b ) p-(a+b) p − ( a + b ) , and so is a differential operator in β \beta β that is generically of the same order.
We have implemented this procedure for all monomials with p = m + n ≤ 7 p=m+n\le7 p = m + n ≤ 7 . The operators D a , b D_{a,b} D a , b that result from this process are listed in Eq. (S18); this table can be read as follows. Each row in Eq. (S18) corresponds to a constraint, at the value of p p p denoted in the first column of that table. The entries in each row list the values of D a , b D_{a,b} D a , b for a + b ≤ p a+b\le p a + b ≤ p in the following ‘dictionary’ order:
( b , a ) = ( 0 , 0 ) , ( 0 , 1 ) , … ( 0 , p ) , ( 1 , 1 ) , ( 1 , 2 ) … ( 1 , p − 1 ) , ( 2 , 2 ) … (74) (b,a)=(0,0),\ (0,1),\ldots(0,p),\ (1,1),\ (1,2)\ldots(1,p-1),\ (2,2)\ldots \tag*{(74)} ( b , a ) = ( 0 , 0 ) , ( 0 , 1 ) , … ( 0 , p ) , ( 1 , 1 ) , ( 1 , 2 ) … ( 1 , p − 1 ) , ( 2 , 2 ) … (74)
In other words we first list D a , b D_{a,b} D a , b with b = 0 b=0 b = 0 and a a a ranging from 0 to p p p . Then we do the same for b = 1 b=1 b = 1 and a a a ranging from 1 to $p-1 and so on. The total number of distinct values of D a , b D_{a,b} D a , b equals
( p + 1 ) + ( p − 1 ) + ( p − 3 ) + … ( p + 1 − 2 ⌊ p + 1 2 ⌋ ) = ⌊ ( p + 2 ) 2 4 ⌋ . (75) (p+1)+(p-1)+(p-3)+\ldots\left(p+1-2\left\lfloor\frac{p+1}{2}\right\rfloor\right)=\left\lfloor\frac{(p+2)^2}{4}\right\rfloor. \tag*{(75)} ( p + 1 ) + ( p − 1 ) + ( p − 3 ) + … ( p + 1 − 2 ⌊ 2 p + 1 ⌋ ) = ⌊ 4 ( p + 2 ) 2 ⌋ . (75)
So we have 4 terms at p = 2 p=2 p = 2 , 9 terms at p = 4 p=4 p = 4 , 12 terms at p = 5 p=5 p = 5 , 16 terms at p = 6 p=6 p = 6 , 20 terms at p = 7 p=7 p = 7 . These terms are all listed in the corresponding rows of Eq. (S18).
As an example of the use of the table Eq. (S18), we use the p = 2 p=2 p = 2 line of this table to read off the form of the constraint at p = 2 p=2 p = 2 , which then takes the form
( θ 2 ) h 0 , 0 + 3 ( θ − 1 1 ) h 1 , 0 + 3 ( h 1 , 1 + h 2 , 0 ) = 0 ⇒ ( β 2 d d β 2 − 1 ) ( β 2 d d β 2 ) h 0 , 0 + 6 ( β 2 d d β 2 − 1 ) h 1 , 0 + 6 ( h 2 , 0 + h 1 , 1 ) = 0 (76) \begin{aligned}
\binom{\theta}{2}h_{0,0}+3\binom{\theta-1}{1}h_{1,0}+3(h_{1,1}+h_{2,0})=0 \\
&\Rightarrow\left(\beta^2\frac{d}{d\beta^2}-1\right)\left(\beta^2\frac{d}{d\beta^2}\right)h_{0,0}+6\left(\beta^2\frac{d}{d\beta^2}-1\right)h_{1,0}+6(h_{2,0}+h_{1,1})=0 \tag*{(76)}
\end{aligned} ( 2 θ ) h 0 , 0 + 3 ( 1 θ − 1 ) h 1 , 0 + 3 ( h 1 , 1 + h 2 , 0 ) = 0 ⇒ ( β 2 d β 2 d − 1 ) ( β 2 d β 2 d ) h 0 , 0 + 6 ( β 2 d β 2 d − 1 ) h 1 , 0 + 6 ( h 2 , 0 + h 1 , 1 ) = 0 (76)
(S17) is in perfect agreement with Eq. (15) of [6 ] after setting a = 0 a=0 a = 0 in that equation (this is appropriate since we are studying ln Z r o t \ln Z^{\mathrm{rot}} ln Z rot rather than ln Z \ln Z ln Z in this section).
Table S18.
As we have explained above, the table Eq. (S18) lists the form of the semi-universal constraints (for p ≤ 7 p \le7 p ≤ 7 ) obtained from the Taylor expansion of Eq. (70) . We now compare these constraints with those obtained using the methods of [6 ] , i.e. by proceeding as follows. We simply plug the expansion Eq. (S.13) of [6 ] into Eq. (17) , and then plug (19) into the resultant equation, and perform the integral over z z z . As the integrand is a polynomial in z z z , the integral is very easy to perform, and yields an H H H function of the form Eq. (72) . While the number of distinct functions h m , n ( β 2 ) h_{m,n}(\beta^2) h m , n ( β 2 ) with m + n = p m+n=p m + n = p equals ⌊ p 2 + 1 ⌋ \left\lfloor\frac{p}{2}+1\right\rfloor ⌊ 2 p + 1 ⌋ , the number of local terms (in Eq. (S.13) of [6 ] ) that contribute to the partition function at this order equals the smaller number ⌊ p 3 + 1 ⌋ \left\lfloor\frac{p}{3}+1\right\rfloor ⌊ 3 p + 1 ⌋ . Summing these numbers, we see that while the number of distinct h m , n ( β 2 ) h_{m,n}(\beta^2) h m , n ( β 2 ) with m + n ≤ p m+n\le p m + n ≤ p equals ⌊ ( p + 2 ) 2 4 ⌋ \left\lfloor\frac{(p+2)^2}{4}\right\rfloor ⌊ 4 ( p + 2 ) 2 ⌋ , the number of local structures (i.e. terms listed in Eq. (S.13) of [6 ] with m + 3 n ≤ p m+3n\le p m + 3 n ≤ p ) equals ⌊ ( p + 2 ) ( p + 3 ) 6 ⌋ \left\lfloor\frac{(p+2)(p+3)}{6}\right\rfloor ⌊ 6 ( p + 2 ) ( p + 3 ) ⌋ .
Consequently, the integral described above can be thought of as generating a rectangular matrix with ⌊ ( p + 2 ) 2 4 ⌋ \left\lfloor\frac{(p+2)^2}{4}\right\rfloor ⌊ 4 ( p + 2 ) 2 ⌋ rows and ⌊ ( p + 2 ) ( p + 3 ) 6 ⌋ \left\lfloor\frac{(p+2)(p+3)}{6}\right\rfloor ⌊ 6 ( p + 2 ) ( p + 3 ) ⌋ columns. The matrix in question acts on the ⌊ ( p + 2 ) ( p + 3 ) 6 ⌋ \left\lfloor\frac{(p+2)(p+3)}{6}\right\rfloor ⌊ 6 ( p + 2 ) ( p + 3 ) ⌋ length column of free local functions that appear in Eq. (S.13) of [6 ] , and creates a ⌊ ( p + 2 ) 2 4 ⌋ \left\lfloor\frac{(p+2)^2}{4}\right\rfloor ⌊ 4 ( p + 2 ) 2 ⌋ length column of functions h m , n ( β 2 ) h_{m,n}(\beta^2) h m , n ( β 2 ) with m + n ≤ p m+n\le p m + n ≤ p .24
Now any matrix with r r r rows and c c c columns has a ‘left null space’ of dimension at least r − c r-c r − c , i.e. an r − c r-c r − c dimensional subspace of rows which, when acting on the matrix from the left simply gives zero. In the situation described above r − c = ⌊ ( p + 2 ) 2 4 ⌋ − ⌊ ( p + 2 ) ( p + 3 ) 6 ⌋ r-c=\left\lfloor\frac{(p+2)^2}{4}\right\rfloor-\left\lfloor\frac{(p+2)(p+3)}{6}\right\rfloor r − c = ⌊ 4 ( p + 2 ) 2 ⌋ − ⌊ 6 ( p + 2 ) ( p + 3 ) ⌋ which > 0 >0 > 0 for p ≥ 2 p\ge2 p ≥ 2 . Consequently, the constraints generated by this method also take the form Eq. (73) , with D a , b D_{a,b} D a , b given by (any arbitrary) basis vectors for this null space. It is easy to convince oneself that if w w w is a null vector of the matrix described above at some p = p ′ p=p' p = p ′ , it remains a null vector at every p ≥ p ′ p\ge p' p ≥ p ′ .
We have used Mathematica to perform the integrals necessary to evaluate the matrices above up to p = 7 p=7 p = 7 , and have determined the explicit form of all left null vectors. Each increase in p p p up to p = 7 p=7 p = 7 increases the dimension of the null space by no more than unity, and we have verified that the row vectors listed in table Eq. (S18) are, indeed, the row vectors that we need to add (to the row vectors listed at every lower level) to correctly generate the null space of the matrix described above at the given value of p p p .
We have thus explicitly verified that the semi-universal constraints that follow from Eq. (64) are identical to those obtained using the methods of [6 ] , at least for p ≤ 7 p\le7 p ≤ 7 .
More about ln Z s h \ln Z^{\mathrm{sh}} ln Z sh
In Eq. (3) we have presented a conjecture for the form of the quantity ln Z s h \ln Z^{\mathrm{sh}} ln Z sh . In this section we explain how we arrived at this conjecture.
The explicit form of the trace of the stress tensor in terms of the various Weyl anomalies is, of course, very well known. By integrating this expression, it is, in principle, not difficult to evaluate ln Z s h \ln Z^{\mathrm{sh}} ln Z sh in any given dimension. However these computations grow increasingly complicated as the dimension is increased. In order to circumvent this complication, we proceeded as follows. We first used Claude Opus 5.5 to compute ln Z s h β \frac{\ln Z^{\mathrm{sh}}}{\beta} β l n Z sh for d d d up to 16 16 16 exactly. From this it proposed the general form Eq. (3) , which reproduced all 65 65 65 exact coefficients for d ≤ 16 d\le16 d ≤ 16 . Finally, we checked this general d d d prediction for d = 18 , 20 d=18,20 d = 18 , 20 numerically to very high precision, again with assistance from Claude Opus 5.5.
In low dimensions, we have also compared the expression in Eq. (3) against results in the published literature. In d = 4 , 6 , 8 d=4,6,8 d = 4 , 6 , 8 , the s s s -integral in the expression for ln Z s h \ln Z^{\mathrm{sh}} ln Z sh in Eq. (3) is easily evaluated, yielding the following more explicit versions of our conjectured expression
ln Z s h β ∣ d = 4 = a 4 12 [ x 1 x 2 + x 2 x 1 + 7 ] \left.\frac{\ln Z^{\mathrm{sh}}}{\beta}\right|_{d=4}=\frac{a_4}{12}\left[\frac{x_1}{x_2}+\frac{x_2}{x_1}+7\right] β ln Z sh d = 4 = 12 a 4 [ x 2 x 1 + x 1 x 2 + 7 ]
ln Z s h β ∣ d = 6 = 3 a 6 80 [ x 1 2 x 2 x 3 + x 2 2 x 1 x 3 + x 3 2 x 1 x 2 − 4 ( x 1 x 2 + x 1 x 3 + x 2 x 1 + x 2 x 3 + x 3 x 1 + x 3 x 2 ) − 29 ] \left.\frac{\ln Z^{\mathrm{sh}}}{\beta}\right|_{d=6}=\frac{3a_6}{80}\left[\frac{x_1^2}{x_2x_3}+\frac{x_2^2}{x_1x_3}+\frac{x_3^2}{x_1x_2}-4\left(\frac{x_1}{x_2}+\frac{x_1}{x_3}+\frac{x_2}{x_1}+\frac{x_2}{x_3}+\frac{x_3}{x_1}+\frac{x_3}{x_2}\right)-29\right] β ln Z sh d = 6 = 80 3 a 6 [ x 2 x 3 x 1 2 + x 1 x 3 x 2 2 + x 1 x 2 x 3 2 − 4 ( x 2 x 1 + x 3 x 1 + x 1 x 2 + x 3 x 2 + x 1 x 3 + x 2 x 3 ) − 29 ]
ln Z s h β ∣ d = 8 = a 8 560 [ 15 ( x 1 3 x 2 x 3 x 4 + x 2 3 x 1 x 3 x 4 + x 3 3 x 1 x 2 x 4 + x 4 3 x 1 x 2 x 3 ) − 55 ( x 1 2 x 2 x 3 + x 1 2 x 2 x 4 + x 1 2 x 3 x 4 + x 2 2 x 1 x 3 + x 2 2 x 1 x 4 + x 2 2 x 3 x 4 + x 3 2 x 1 x 2 + x 3 2 x 1 x 4 + x 3 2 x 2 x 4 + x 4 2 x 1 x 2 + x 4 2 x 1 x 3 + x 4 2 x 2 x 3 ) + 29 ( x 1 x 2 x 3 x 4 + x 1 x 3 x 2 x 4 + x 1 x 4 x 2 x 3 + x 2 x 3 x 1 x 4 + x 2 x 4 x 1 x 3 + x 3 x 4 x 1 x 2 ) + 211 ( x 1 x 2 + x 1 x 3 + x 1 x 4 + x 2 x 1 + x 2 x 3 + x 2 x 4 + x 3 x 1 + x 3 x 2 + x 3 x 4 + x 4 x 1 + x 4 x 2 + x 4 x 3 ) + 1569 ] . (77) \begin{aligned}
\left.\frac{\ln Z^{\mathrm{sh}}}{\beta}\right|_{d=8}
={}&\frac{a_8}{560}\Bigg[15\left(\frac{x_1^3}{x_2x_3x_4}+\frac{x_2^3}{x_1x_3x_4}+\frac{x_3^3}{x_1x_2x_4}+\frac{x_4^3}{x_1x_2x_3}\right)\\
&-55\left(\frac{x_1^2}{x_2x_3}+\frac{x_1^2}{x_2x_4}+\frac{x_1^2}{x_3x_4}+\frac{x_2^2}{x_1x_3}+\frac{x_2^2}{x_1x_4}+\frac{x_2^2}{x_3x_4}+\frac{x_3^2}{x_1x_2}+\frac{x_3^2}{x_1x_4}+\frac{x_3^2}{x_2x_4}+\frac{x_4^2}{x_1x_2}+\frac{x_4^2}{x_1x_3}+\frac{x_4^2}{x_2x_3}\right)\\
&+29\left(\frac{x_1x_2}{x_3x_4}+\frac{x_1x_3}{x_2x_4}+\frac{x_1x_4}{x_2x_3}+\frac{x_2x_3}{x_1x_4}+\frac{x_2x_4}{x_1x_3}+\frac{x_3x_4}{x_1x_2}\right)\\
&+211\left(\frac{x_1}{x_2}+\frac{x_1}{x_3}+\frac{x_1}{x_4}+\frac{x_2}{x_1}+\frac{x_2}{x_3}+\frac{x_2}{x_4}+\frac{x_3}{x_1}+\frac{x_3}{x_2}+\frac{x_3}{x_4}+\frac{x_4}{x_1}+\frac{x_4}{x_2}+\frac{x_4}{x_3}\right)+1569\Bigg]. \tag*{(77)}
\end{aligned} β ln Z sh d = 8 = 560 a 8 [ 15 ( x 2 x 3 x 4 x 1 3 + x 1 x 3 x 4 x 2 3 + x 1 x 2 x 4 x 3 3 + x 1 x 2 x 3 x 4 3 ) − 55 ( x 2 x 3 x 1 2 + x 2 x 4 x 1 2 + x 3 x 4 x 1 2 + x 1 x 3 x 2 2 + x 1 x 4 x 2 2 + x 3 x 4 x 2 2 + x 1 x 2 x 3 2 + x 1 x 4 x 3 2 + x 2 x 4 x 3 2 + x 1 x 2 x 4 2 + x 1 x 3 x 4 2 + x 2 x 3 x 4 2 ) + 29 ( x 3 x 4 x 1 x 2 + x 2 x 4 x 1 x 3 + x 2 x 3 x 1 x 4 + x 1 x 4 x 2 x 3 + x 1 x 3 x 2 x 4 + x 1 x 2 x 3 x 4 ) + 211 ( x 2 x 1 + x 3 x 1 + x 4 x 1 + x 1 x 2 + x 3 x 2 + x 4 x 2 + x 1 x 3 + x 2 x 3 + x 4 x 3 + x 1 x 4 + x 2 x 4 + x 3 x 4 ) + 1569 ] . (77)
The above three expressions for d = 4 , 6 , 8 d=4,6,8 d = 4 , 6 , 8 match exactly with the equations (44), (45) and (49)15 of the paper [49 ] . It should be noted that ln Z s h β ∣ d = 4 , 6 , 8 = E v a c ( d = 4 , 6 , 8 ) \left.\frac{\ln Z^{\mathrm{sh}}}{\beta}\right|_{d=4,6,8}=E_{\mathrm{vac}}^{(d=4,6,8)} β l n Z sh d = 4 , 6 , 8 = E vac ( d = 4 , 6 , 8 ) in the convention of [49 ] and a 4 = π 2 48 G 5 a_4=\frac{\pi^2}{48G_5} a 4 = 48 G 5 π 2 , a 6 = π 3 48 G 7 a_6=\frac{\pi^3}{48G_7} a 6 = 48 G 7 π 3 , a 8 = π 4 576 G 9 a_8=\frac{\pi^4}{576G_9} a 8 = 576 G 9 π 4 as explained in Eq. (224) .
The Z κ + 1 Z_{\kappa+1} Z κ + 1 orbit sum over ( ln Z s h ) / β (\ln Z^{\mathrm{sh}})/\beta ( ln Z sh ) / β
In this section we evaluate the orbit sum of ln Z s h β \frac{\ln Z^{\mathrm{sh}}}{\beta} β l n Z sh for a general κ \kappa κ . In terms of the variables b i b_i b i for i = 0 , 1 , … , κ i=0,1,\ldots,\kappa i = 0 , 1 , … , κ , the expression becomes
ln Z s h β = κ ! a 2 κ [ ( − 1 ) κ + 1 2 2 κ − 1 ∑ i = 0 κ ∫ 0 1 d s ∏ j = 1 j ≠ i κ [ ( s − 2 ) b 0 2 + 2 b j 2 − s b i 2 ] 2 ( b 0 2 − b j 2 ) ( b j 2 − b i 2 ) ] . (78) \frac{\ln Z^{\mathrm{sh}}}{\beta}=\kappa!a_{2\kappa}\left[(-1)^\kappa+\frac{1}{2^{2\kappa-1}}\sum_{i=0}^{\kappa}\int_0^1 ds\prod_{\substack{j=1\\j\ne i}}^\kappa\frac{\left[(s-2)b_0^2+2b_j^2-sb_i^2\right]^2}{(b_0^2-b_j^2)(b_j^2-b_i^2)}\right]. \tag*{(78)} β ln Z sh = κ ! a 2 κ ( − 1 ) κ + 2 2 κ − 1 1 i = 0 ∑ κ ∫ 0 1 d s j = 1 j = i ∏ κ ( b 0 2 − b j 2 ) ( b j 2 − b i 2 ) [ ( s − 2 ) b 0 2 + 2 b j 2 − s b i 2 ] 2 . (78)
Applying Ω p \Omega^p Ω p on the above equation, we get
Ω p ∘ [ ln Z s h β ] = κ ! a 2 κ [ ( − 1 ) κ + 1 2 2 κ − 1 ∑ i = 0 κ ∫ 0 1 d s ∏ j = 0 j ≠ i , p κ [ ( s − 2 ) b p 2 + 2 b j 2 − s b i 2 ] 2 ( b p 2 − b j 2 ) ( b j 2 − b i 2 ) ] , for p = 0 , 1 , … , κ . (79) \Omega^p\circ\left[\frac{\ln Z^{\mathrm{sh}}}{\beta}\right]=\kappa!a_{2\kappa}\left[(-1)^\kappa+\frac{1}{2^{2\kappa-1}}\sum_{i=0}^{\kappa}\int_0^1 ds\prod_{\substack{j=0\\j\ne i,p}}^\kappa\frac{\left[(s-2)b_p^2+2b_j^2-sb_i^2\right]^2}{(b_p^2-b_j^2)(b_j^2-b_i^2)}\right],\qquad\text{for }p=0,1,\ldots,\kappa. \tag*{(79)} Ω p ∘ [ β ln Z sh ] = κ ! a 2 κ ( − 1 ) κ + 2 2 κ − 1 1 i = 0 ∑ κ ∫ 0 1 d s j = 0 j = i , p ∏ κ ( b p 2 − b j 2 ) ( b j 2 − b i 2 ) [ ( s − 2 ) b p 2 + 2 b j 2 − s b i 2 ] 2 , for p = 0 , 1 , … , κ . (79)
Before going into the actual proof, we will define notation. Set
Q ( z ) : = ∏ i = 0 κ ( z − b i 2 ) , L i ( z ) : = ∏ j = 0 j ≠ i κ z − b j 2 b i 2 − b j 2 = Q ( z ) ( z − b i 2 ) Q ′ ( b i 2 ) . (80) Q(z):=\prod_{i=0}^{\kappa}(z-b_i^2),\qquad L_i(z):=\prod_{\substack{j=0\\j\ne i}}^\kappa\frac{z-b_j^2}{b_i^2-b_j^2}=\frac{Q(z)}{(z-b_i^2)Q'(b_i^2)}. \tag*{(80)} Q ( z ) := i = 0 ∏ κ ( z − b i 2 ) , L i ( z ) := j = 0 j = i ∏ κ b i 2 − b j 2 z − b j 2 = ( z − b i 2 ) Q ′ ( b i 2 ) Q ( z ) . (80)
so that L i ( z ) L_i(z) L i ( z ) is a basis (Lagrange basis) polynomial, with L i ( b j 2 ) = δ i j L_i(b_j^2)=\delta_{ij} L i ( b j 2 ) = δ ij . We will apply the residue theorem to the following function
f ( ζ ) = 1 ( z − ζ ) Q ( ζ ) . (81) f(\zeta)=\frac{1}{(z-\zeta)Q(\zeta)}. \tag*{(81)} f ( ζ ) = ( z − ζ ) Q ( ζ ) 1 . (81)
Its residues are 1 ( z − b i 2 ) Q ′ ( b i 2 ) \frac{1}{(z-b_i^2)Q'(b_i^2)} ( z − b i 2 ) Q ′ ( b i 2 ) 1 at ζ = b i 2 \zeta=b_i^2 ζ = b i 2 and − 1 Q ( z ) -\frac{1}{Q(z)} − Q ( z ) 1 at ζ = z ≠ b i 2 \zeta=z\ne b_i^2 ζ = z = b i 2 for all i = 0 , 1 , ⋯ , κ i=0,1,\cdots,\kappa i = 0 , 1 , ⋯ , κ . The residue at infinity vanishes because f ( ζ ) ∼ − ζ − κ − 2 f(\zeta)\sim-\zeta^{-\kappa-2} f ( ζ ) ∼ − ζ − κ − 2 . Since the residues sum to zero,
∑ i = 0 κ L i ( z ) = 1. (82) \sum_{i=0}^{\kappa}L_i(z)=1 . \tag*{(82)} i = 0 ∑ κ L i ( z ) = 1. (82)
Now consider the distinguished variable in slot p p p (for ln Z s h β \frac{\ln Z^{\mathrm{sh}}}{\beta} β l n Z sh itself, p = 0 p=0 p = 0 ), take i ≠ p i\ne p i = p , and define
z = b p 2 + s 2 ( b i 2 − b p 2 ) . (83) z=b_p^2+\frac{s}{2}(b_i^2-b_p^2). \tag*{(83)} z = b p 2 + 2 s ( b i 2 − b p 2 ) . (83)
The integration range of s s s from 0 to 1, becomes the range of z z z from b p 2 b_p^2 b p 2 to 1 2 ( b p 2 + b i 2 ) \frac{1}{2}(b_p^2+b_i^2) 2 1 ( b p 2 + b i 2 ) . Then
( s − 2 ) b p 2 + 2 b i 2 − s b i 2 = 2 ( b i 2 − z ) , (84) (s-2)b_p^2+2b_i^2-sb_i^2=2(b_i^2-z), \tag*{(84)} ( s − 2 ) b p 2 + 2 b i 2 − s b i 2 = 2 ( b i 2 − z ) , (84)
∏ j ≠ p , i ( b j 2 − z ) 2 = Q ( z ) 2 ( z − b p 2 ) 2 ( z − b i 2 ) 2 , (85) \prod_{j\ne p,i}(b_j^2-z)^2=\frac{Q(z)^2}{(z-b_p^2)^2(z-b_i^2)^2}, \tag*{(85)} j = p , i ∏ ( b j 2 − z ) 2 = ( z − b p 2 ) 2 ( z − b i 2 ) 2 Q ( z ) 2 , (85)
∏ j ≠ p , i ( b p 2 − b j 2 ) ( b j 2 − b i 2 ) = ( − 1 ) κ Q ′ ( b p 2 ) Q ′ ( b i 2 ) ( b i 2 − b p 2 ) 2 . (86) \prod_{j\ne p,i}(b_p^2-b_j^2)(b_j^2-b_i^2)=(-1)^\kappa\frac{Q'(b_p^2)Q'(b_i^2)}{(b_i^2-b_p^2)^2}. \tag*{(86)} j = p , i ∏ ( b p 2 − b j 2 ) ( b j 2 − b i 2 ) = ( − 1 ) κ ( b i 2 − b p 2 ) 2 Q ′ ( b p 2 ) Q ′ ( b i 2 ) . (86)
The integrand of (S21) therefore becomes
1 2 2 κ − 1 ∏ j ≠ p , i [ ( s − 2 ) b p 2 + 2 b j 2 − s b i 2 ] 2 ( b p 2 − b j 2 ) ( b j 2 − b i 2 ) = ( − 1 ) κ 2 ( b i 2 − b p 2 ) 2 L p ( z ) L i ( z ) ( z − b p 2 ) ( z − b i 2 ) . (87) \frac{1}{2^{2\kappa-1}}\prod_{j\ne p,i}\frac{\left[(s-2)b_p^2+2b_j^2-sb_i^2\right]^2}{(b_p^2-b_j^2)(b_j^2-b_i^2)}
=\frac{(-1)^\kappa}{2}(b_i^2-b_p^2)^2\frac{L_p(z)L_i(z)}{(z-b_p^2)(z-b_i^2)}. \tag*{(87)} 2 2 κ − 1 1 j = p , i ∏ ( b p 2 − b j 2 ) ( b j 2 − b i 2 ) [ ( s − 2 ) b p 2 + 2 b j 2 − s b i 2 ] 2 = 2 ( − 1 ) κ ( b i 2 − b p 2 ) 2 ( z − b p 2 ) ( z − b i 2 ) L p ( z ) L i ( z ) . (87)
Changing variables with d s = 2 d z / ( b i 2 − b p 2 ) ds=2\,dz/(b_i^2-b_p^2) d s = 2 d z / ( b i 2 − b p 2 ) , the prefactor 1 2 \frac{1}{2} 2 1 cancels completely, and using partial fraction decomposition of b i 2 − b p 2 ( z − b p 2 ) ( z − b i 2 ) \frac{b_i^2-b_p^2}{(z-b_p^2)(z-b_i^2)} ( z − b p 2 ) ( z − b i 2 ) b i 2 − b p 2 , we get
1 2 2 κ − 1 ∫ 0 1 d s ∏ j ≠ i , p [ ( s − 2 ) b p 2 + 2 b j 2 − s b i 2 ] 2 ( b p 2 − b j 2 ) ( b j 2 − b i 2 ) = ( − 1 ) κ ∫ b p 2 1 2 ( b p 2 + b i 2 ) d z L p ( z ) L i ( z ) [ 1 z − b i 2 − 1 z − b p 2 ] . (88) \frac{1}{2^{2\kappa-1}}\int_0^1ds\prod_{j\ne i,p}\frac{\left[(s-2)b_p^2+2b_j^2-sb_i^2\right]^2}{(b_p^2-b_j^2)(b_j^2-b_i^2)}
=(-1)^\kappa\int_{b_p^2}^{\frac{1}{2}(b_p^2+b_i^2)}dz\,L_p(z)L_i(z)\left[\frac{1}{z-b_i^2}-\frac{1}{z-b_p^2}\right]. \tag*{(88)} 2 2 κ − 1 1 ∫ 0 1 d s j = i , p ∏ ( b p 2 − b j 2 ) ( b j 2 − b i 2 ) [ ( s − 2 ) b p 2 + 2 b j 2 − s b i 2 ] 2 = ( − 1 ) κ ∫ b p 2 2 1 ( b p 2 + b i 2 ) d z L p ( z ) L i ( z ) [ z − b i 2 1 − z − b p 2 1 ] . (88)
We will use the following identity
L i ′ ( z ) L i ( z ) = Q ′ ( z ) Q ( z ) − 1 z − b i 2 , for i = 0 , 1 , ⋯ , κ . (89) \frac{L_i'(z)}{L_i(z)}=\frac{Q'(z)}{Q(z)}-\frac{1}{z-b_i^2},\qquad\text{for }i=0,1,\cdots,\kappa. \tag*{(89)} L i ( z ) L i ′ ( z ) = Q ( z ) Q ′ ( z ) − z − b i 2 1 , for i = 0 , 1 , ⋯ , κ . (89)
So we can write
1 2 2 κ − 1 ∫ 0 1 d s ∏ j ≠ i , p [ ( s − 2 ) b p 2 + 2 b j 2 − s b i 2 ] 2 ( b p 2 − b j 2 ) ( b j 2 − b i 2 ) = ( − 1 ) κ ∫ b p 2 1 2 ( b p 2 + b i 2 ) d z [ L p ′ ( z ) L i ( z ) − L p ( z ) L i ′ ( z ) ] . (90) \frac{1}{2^{2\kappa-1}}\int_0^1ds\prod_{j\ne i,p}\frac{\left[(s-2)b_p^2+2b_j^2-sb_i^2\right]^2}{(b_p^2-b_j^2)(b_j^2-b_i^2)}
=(-1)^\kappa\int_{b_p^2}^{\frac{1}{2}(b_p^2+b_i^2)}dz\,\left[L_p'(z)L_i(z)-L_p(z)L_i'(z)\right]. \tag*{(90)} 2 2 κ − 1 1 ∫ 0 1 d s j = i , p ∏ ( b p 2 − b j 2 ) ( b j 2 − b i 2 ) [ ( s − 2 ) b p 2 + 2 b j 2 − s b i 2 ] 2 = ( − 1 ) κ ∫ b p 2 2 1 ( b p 2 + b i 2 ) d z [ L p ′ ( z ) L i ( z ) − L p ( z ) L i ′ ( z ) ] . (90)
We will sum the indices i , p i,p i , p in the above equation and get
∑ i , p i ≠ p 1 2 2 κ − 1 ∫ 0 1 d s ∏ j ≠ i , p [ ( s − 2 ) b p 2 + 2 b j 2 − s b i 2 ] 2 ( b p 2 − b j 2 ) ( b j 2 − b i 2 ) = ( − 1 ) κ 2 ∑ i , p i ≠ p [ ∫ b p 2 1 2 ( b p 2 + b i 2 ) d z [ L p ′ ( z ) L i ( z ) − L p ( z ) L i ′ ( z ) ] + ∫ b i 2 1 2 ( b p 2 + b i 2 ) d z [ L i ′ ( z ) L p ( z ) − L i ( z ) L p ′ ( z ) ] ] = ( − 1 ) κ 2 ∑ i , p i ≠ p ∫ b p 2 b i 2 d z [ L p ′ ( z ) L i ( z ) − L p ( z ) L i ′ ( z ) ] = ( − 1 ) κ ∑ i , p = 0 κ ∫ b p 2 b i 2 d z L p ′ ( z ) L i ( z ) . (91) \begin{aligned}
\sum_{\substack{i,p\\i\ne p}}\frac{1}{2^{2\kappa-1}}\int_0^1ds\prod_{j\ne i,p}\frac{\left[(s-2)b_p^2+2b_j^2-sb_i^2\right]^2}{(b_p^2-b_j^2)(b_j^2-b_i^2)}
={}&\frac{(-1)^\kappa}{2}\sum_{\substack{i,p\\i\ne p}}\left[\int_{b_p^2}^{\frac{1}{2}(b_p^2+b_i^2)}dz\,\left[L_p'(z)L_i(z)-L_p(z)L_i'(z)\right]\right.\\
&\left.+\int_{b_i^2}^{\frac{1}{2}(b_p^2+b_i^2)}dz\,\left[L_i'(z)L_p(z)-L_i(z)L_p'(z)\right]\right]\\
={}&\frac{(-1)^\kappa}{2}\sum_{\substack{i,p\\i\ne p}}\int_{b_p^2}^{b_i^2}dz\,\left[L_p'(z)L_i(z)-L_p(z)L_i'(z)\right]\\
={}&(-1)^\kappa\sum_{i,p=0}^{\kappa}\int_{b_p^2}^{b_i^2}dz\,L_p'(z)L_i(z). \tag*{(91)}
\end{aligned} i , p i = p ∑ 2 2 κ − 1 1 ∫ 0 1 d s j = i , p ∏ ( b p 2 − b j 2 ) ( b j 2 − b i 2 ) [ ( s − 2 ) b p 2 + 2 b j 2 − s b i 2 ] 2 = = = 2 ( − 1 ) κ i , p i = p ∑ [ ∫ b p 2 2 1 ( b p 2 + b i 2 ) d z [ L p ′ ( z ) L i ( z ) − L p ( z ) L i ′ ( z ) ] + ∫ b i 2 2 1 ( b p 2 + b i 2 ) d z [ L i ′ ( z ) L p ( z ) − L i ( z ) L p ′ ( z ) ] ] 2 ( − 1 ) κ i , p i = p ∑ ∫ b p 2 b i 2 d z [ L p ′ ( z ) L i ( z ) − L p ( z ) L i ′ ( z ) ] ( − 1 ) κ i , p = 0 ∑ κ ∫ b p 2 b i 2 d z L p ′ ( z ) L i ( z ) . (91)
where in the second step of the manipulation, we have symmetrized the index ( i , p ) (i,p) ( i , p ) by introducing a half factor in front and in the third step, we have eliminated the upper limit 1 2 ( b p 2 + b i 2 ) \frac{1}{2}(b_p^2+b_i^2) 2 1 ( b p 2 + b i 2 ) from the two integrals. The constraint i ≠ p i\ne p i = p goes away because the summand for i = p i=p i = p in the third step vanishes. Consider the summand integral and split it at z = c ≠ b i 2 z=c\ne b_i^2 z = c = b i 2 such that
∫ b p 2 b i 2 d z L p ′ ( z ) L i ( z ) = ∫ c b i 2 d z L p ′ ( z ) L i ( z ) − ∫ c b p 2 d z L p ′ ( z ) L i ( z ) . (92) \int_{b_p^2}^{b_i^2} \mathrm{d}z\,L_p'(z)L_i(z)=\int_c^{b_i^2}\mathrm{d}z\,L_p'(z)L_i(z)-\int_c^{b_p^2}\mathrm{d}z\,L_p'(z)L_i(z). \tag*{(92)} ∫ b p 2 b i 2 d z L p ′ ( z ) L i ( z ) = ∫ c b i 2 d z L p ′ ( z ) L i ( z ) − ∫ c b p 2 d z L p ′ ( z ) L i ( z ) . (92)
Hence the summation can be written as
∑ i , p = 0 κ ∫ b p 2 b i 2 d z L p ′ ( z ) L i ( z ) = ∑ i = 0 κ ∫ c b i 2 d z ( ∑ p = 0 κ L p ( z ) ) ′ L i ( z ) − ∑ p = 0 κ ∫ c b p 2 d z L p ′ ( z ) ( ∑ i = 0 κ L i ( z ) ) = 0 − ∑ p = 0 κ [ L p ( b p 2 ) − L p ( c ) ] = − κ . (93) \begin{aligned}
\sum_{i,p=0}^{\kappa}\int_{b_p^2}^{b_i^2}\mathrm{d}z\,L_p'(z)L_i(z)=\sum_{i=0}^{\kappa}\int_c^{b_i^2}\mathrm{d}z\left(\sum_{p=0}^{\kappa}L_p(z)\right)'L_i(z)-\sum_{p=0}^{\kappa}\int_c^{b_p^2}\mathrm{d}z\,L_p'(z)\left(\sum_{i=0}^{\kappa}L_i(z)\right) \\
&=0-\sum_{p=0}^{\kappa}\left[L_p(b_p^2)-L_p(c)\right]=-\kappa. \tag*{(93)}
\end{aligned} i , p = 0 ∑ κ ∫ b p 2 b i 2 d z L p ′ ( z ) L i ( z ) = i = 0 ∑ κ ∫ c b i 2 d z ( p = 0 ∑ κ L p ( z ) ) ′ L i ( z ) − p = 0 ∑ κ ∫ c b p 2 d z L p ′ ( z ) ( i = 0 ∑ κ L i ( z ) ) = 0 − p = 0 ∑ κ [ L p ( b p 2 ) − L p ( c ) ] = − κ . (93)
Summing over p p p in Eq. (79) , we have
( 1 + Ω + ⋯ + Ω κ ) ∘ [ ln Z s h β ] = ( − 1 ) κ κ ! a 2 κ ( κ + 1 − κ ) = ( − 1 ) κ κ ! a 2 κ , (94) \left(1+\Omega+\cdots+\Omega^\kappa\right)\circ\left[\frac{\ln Z^{\mathrm{sh}}}{\beta}\right]=(-1)^\kappa\kappa!a_{2\kappa}(\kappa+1-\kappa)=(-1)^\kappa\kappa!a_{2\kappa}, \tag*{(94)} ( 1 + Ω + ⋯ + Ω κ ) ∘ [ β ln Z sh ] = ( − 1 ) κ κ ! a 2 κ ( κ + 1 − κ ) = ( − 1 ) κ κ ! a 2 κ , (94)
which is our cyclic identity for the anomalous part.
Simple symmetrization identities
In the last step in Eq. (26) we have used
3 S ∘ ( b 1 2 − b 2 2 ) = ( b 1 2 − b 2 2 ) + ( b 2 2 − b 0 2 ) + ( b 0 2 − b 1 2 ) = 0 , 3\mathfrak{S}\circ(b_1^2-b_2^2)=(b_1^2-b_2^2)+(b_2^2-b_0^2)+(b_0^2-b_1^2)=0, 3 S ∘ ( b 1 2 − b 2 2 ) = ( b 1 2 − b 2 2 ) + ( b 2 2 − b 0 2 ) + ( b 0 2 − b 1 2 ) = 0 ,
3 S ∘ ( b 1 2 b 0 2 − b 2 2 b 0 2 ) = ( b 1 2 b 0 2 − b 2 2 b 0 2 ) + ( b 2 2 b 1 2 − b 0 2 b 1 2 ) + ( b 0 2 b 2 2 − b 1 2 b 2 2 ) = 0 , 3\mathfrak{S}\circ(b_1^2b_0^2-b_2^2b_0^2)=(b_1^2b_0^2-b_2^2b_0^2)+(b_2^2b_1^2-b_0^2b_1^2)+(b_0^2b_2^2-b_1^2b_2^2)=0, 3 S ∘ ( b 1 2 b 0 2 − b 2 2 b 0 2 ) = ( b 1 2 b 0 2 − b 2 2 b 0 2 ) + ( b 2 2 b 1 2 − b 0 2 b 1 2 ) + ( b 0 2 b 2 2 − b 1 2 b 2 2 ) = 0 ,
3 S ∘ ( b 1 2 b 0 4 − b 2 2 b 0 4 ) = ( b 1 2 b 0 4 − b 2 2 b 0 4 ) + ( b 2 2 b 1 4 − b 0 2 b 1 4 ) + ( b 0 2 b 2 4 − b 1 2 b 2 4 ) = − ( b 0 2 − b 1 2 ) ( b 1 2 − b 2 2 ) ( b 2 2 − b 0 2 ) = − 2 π 2 P . (95) 3\mathfrak{S}\circ(b_1^2b_0^4-b_2^2b_0^4)=(b_1^2b_0^4-b_2^2b_0^4)+(b_2^2b_1^4-b_0^2b_1^4)+(b_0^2b_2^4-b_1^2b_2^4)=-(b_0^2-b_1^2)(b_1^2-b_2^2)(b_2^2-b_0^2)=-\frac{2\pi^2}{P}. \tag*{(95)} 3 S ∘ ( b 1 2 b 0 4 − b 2 2 b 0 4 ) = ( b 1 2 b 0 4 − b 2 2 b 0 4 ) + ( b 2 2 b 1 4 − b 0 2 b 1 4 ) + ( b 0 2 b 2 4 − b 1 2 b 2 4 ) = − ( b 0 2 − b 1 2 ) ( b 1 2 − b 2 2 ) ( b 2 2 − b 0 2 ) = − P 2 π 2 . (95)
Equating the coefficients of distinct powers of β 2 q \beta^{2q} β 2 q in the last of Eq. (26) yields Eq. (40) .
The vanishing of I q ( κ ) I_q^{(\kappa)} I q ( κ ) in 2 κ 2\kappa 2 κ dimensions for κ ≥ 2 \kappa\ge2 κ ≥ 2
In this Appendix we will demonstrate that the first of Eq. (6) implies Eq. (40) is true in arbitrary even dimensions, i.e. at arbitrary integer values of κ \kappa κ . From (3) it follows that
ln Z r o t β = − 1 ∏ i = 1 κ ( b 0 2 − b i 2 ) ( ∑ q = 0 ∞ T q ) . (96) \frac{\ln Z^{\mathrm{rot}}}{\beta}=-\frac{1}{\prod_{i=1}^{\kappa}(b_0^2-b_i^2)}\left(\sum_{q=0}^{\infty}T_q\right). \tag*{(96)} β ln Z rot = − ∏ i = 1 κ ( b 0 2 − b i 2 ) 1 ( q = 0 ∑ ∞ T q ) . (96)
The denominator in (S38) does not transform in a particularly simple manner under either Z κ + 1 \mathbb{Z}_{\kappa+1} Z κ + 1 or the full S κ + 1 \mathbb{S}_{\kappa+1} S κ + 1 permutation group. We can fix this by multiplying the numerator and denominator of this expression by
V 0 = det ( 1 1 ⋯ 1 b 1 2 b 2 2 ⋯ b κ 2 ⋮ ⋮ ⋱ ⋮ b 1 2 ( κ − 1 ) b 2 2 ( κ − 1 ) ⋯ b κ 2 ( κ − 1 ) ) = ∏ 1 ≤ i < j ≤ κ ( b j 2 − b i 2 ) . (97) \mathcal{V}_0=\det\begin{pmatrix}
1 & 1 & \cdots& 1\\
b_1^2 & b_2^2 & \cdots& b_\kappa^2\\
\vdots& \vdots& \ddots& \vdots\\
b_1^{2(\kappa-1)} & b_2^{2(\kappa-1)} & \cdots& b_\kappa^{2(\kappa-1)}
\end{pmatrix}=\prod_{1\le i<j\le\kappa}(b_j^2-b_i^2). \tag*{(97)} V 0 = det 1 b 1 2 ⋮ b 1 2 ( κ − 1 ) 1 b 2 2 ⋮ b 2 2 ( κ − 1 ) ⋯ ⋯ ⋱ ⋯ 1 b κ 2 ⋮ b κ 2 ( κ − 1 ) = 1 ≤ i < j ≤ κ ∏ ( b j 2 − b i 2 ) . (97)
On doing this, (S38) can be rewritten as
ln Z r o t β = ( − 1 ) κ + 1 V ( ∑ q = 0 ∞ V 0 T q ) , (98) \frac{\ln Z^{\mathrm{rot}}}{\beta}=\frac{(-1)^{\kappa+1}}{\mathcal{V}}\left(\sum_{q=0}^{\infty}\mathcal{V}_0T_q\right), \tag*{(98)} β ln Z rot = V ( − 1 ) κ + 1 ( q = 0 ∑ ∞ V 0 T q ) , (98)
where the denominator is now the Vandermonde
V = det ( 1 1 ⋯ 1 b 0 2 b 1 2 ⋯ b κ 2 ⋮ ⋮ ⋱ ⋮ b 0 2 κ b 1 2 κ ⋯ b κ 2 κ ) = ∏ 0 ≤ i < j ≤ κ ( b j 2 − b i 2 ) . (99) \mathcal{V}=\det\begin{pmatrix}
1 & 1 & \cdots& 1 \\
b_0^2 & b_1^2 & \cdots& b_\kappa^2 \\
\vdots& \vdots& \ddots& \vdots\\
b_0^{2\kappa} & b_1^{2\kappa} & \cdots& b_\kappa^{2\kappa}
\end{pmatrix}
=\prod_{0\le i<j\le\kappa}(b_j^2-b_i^2). \tag*{(99)} V = det 1 b 0 2 ⋮ b 0 2 κ 1 b 1 2 ⋮ b 1 2 κ ⋯ ⋯ ⋱ ⋯ 1 b κ 2 ⋮ b κ 2 κ = 0 ≤ i < j ≤ κ ∏ ( b j 2 − b i 2 ) . (99)
which lies in the completely antisymmetric representation of S κ + 1 S_{\kappa+1} S κ + 1 . Ω \Omega Ω , the Z κ + 1 \mathbb{Z}_{\kappa+1} Z κ + 1 generator, can be thought of as a product of κ \kappa κ interchanges, and so its action on the completely antisymmetric object V \mathcal{V} V is given by
Ω ∘ V = ( − 1 ) κ V . (100) \Omega\circ\mathcal{V}=(-1)^\kappa\mathcal{V}. \tag*{(100)} Ω ∘ V = ( − 1 ) κ V . (100)
For later use we also define
V a = ∏ 0 ≤ i < j ≤ κ i , j ≠ a ( b j 2 − b i 2 ) . (101) \mathcal{V}_a=\prod_{\substack{0\le i<j\le\kappa\\i,j\ne a}}(b_j^2-b_i^2). \tag*{(101)} V a = 0 ≤ i < j ≤ κ i , j = a ∏ ( b j 2 − b i 2 ) . (101)
Inserting (10) into (S40) we see that ln Z r o t β \frac{\ln Z^{\mathrm{rot}}}{\beta} β l n Z rot can be written as
ln Z r o t β = ( − 1 ) κ + 1 V ( ∑ q = 0 ∞ V 0 ( ∑ m = 0 κ b 0 2 m I q ( m ) ) ) . (102) \frac{\ln Z^{\mathrm{rot}}}{\beta}=\frac{(-1)^{\kappa+1}}{\mathcal{V}}\left(\sum_{q=0}^{\infty}\mathcal{V}_0\left(\sum_{m=0}^{\kappa}b_0^{2m}I_q^{(m)}\right)\right). \tag*{(102)} β ln Z rot = V ( − 1 ) κ + 1 ( q = 0 ∑ ∞ V 0 ( m = 0 ∑ κ b 0 2 m I q ( m ) ) ) . (102)
We now insert (S40) into (7). Using (S42), the permutation invariance of I q ( m ) I_q^{(m)} I q ( m ) , we obtain
Ω a ∘ [ V 0 V ] = ( − 1 ) a V a V , (103) \Omega^a\circ\left[\frac{\mathcal{V}_0}{\mathcal{V}}\right]=(-1)^a\frac{\mathcal{V}_a}{\mathcal{V}}, \tag*{(103)} Ω a ∘ [ V V 0 ] = ( − 1 ) a V V a , (103)
G ∘ [ ln Z r o t β ] = ( − 1 ) κ + 1 V ( κ + 1 ) ∑ q = 0 ∞ ∑ m = 0 κ ∑ a = 0 κ [ V a ( − 1 ) a I q ( m ) b a 2 m ] . (104) \mathcal{G}\circ\left[\frac{\ln Z^{\mathrm{rot}}}{\beta}\right]=\frac{(-1)^{\kappa+1}}{\mathcal{V}(\kappa+1)}\sum_{q=0}^{\infty}\sum_{m=0}^{\kappa}\sum_{a=0}^{\kappa}\left[\mathcal{V}_a(-1)^a I_q^{(m)}b_a^{2m}\right]. \tag*{(104)} G ∘ [ β ln Z rot ] = V ( κ + 1 ) ( − 1 ) κ + 1 q = 0 ∑ ∞ m = 0 ∑ κ a = 0 ∑ κ [ V a ( − 1 ) a I q ( m ) b a 2 m ] . (104)
Where
G = 1 κ + 1 ∑ a = 0 κ Ω a . (105) \mathcal{G}=\frac{1}{\kappa+1}\sum_{a=0}^{\kappa}\Omega^a. \tag*{(105)} G = κ + 1 1 a = 0 ∑ κ Ω a . (105)
Now recall that any n × n n\times n n × n matrix A i j A_{ij} A ij obeys the identity
∑ j = 1 n ( − 1 ) j + n A m j A ^ n j = δ m n det ( A ) (106) \sum_{j=1}^{n}(-1)^{j+n}A_{mj}\widehat{A}_{nj}=\delta_{mn}\det(A) \tag*{(106)} j = 1 ∑ n ( − 1 ) j + n A mj A nj = δ mn det ( A ) (106)
where A ^ i j \widehat{A}_{ij} A ij is the minor of the element A i j A_{ij} A ij . Applying the identity (S48) to the matrix listed in (S41) with m = 0 , 1 , 2 , … , κ − 1 m=0,1,2,\ldots,\kappa-1 m = 0 , 1 , 2 , … , κ − 1 and n = κ n=\kappa n = κ we obtain
∑ a = 0 κ b a 2 n V a ( − 1 ) a = 0 ( n = 0 , 1 , 2 , … , κ − 1 ) . (107) \sum_{a=0}^{\kappa}b_a^{2n}\mathcal{V}_a(-1)^a=0\qquad(n=0,1,2,\ldots,\kappa-1). \tag*{(107)} a = 0 ∑ κ b a 2 n V a ( − 1 ) a = 0 ( n = 0 , 1 , 2 , … , κ − 1 ) . (107)
Applying the same identity with m = κ m=\kappa m = κ gives
∑ a = 0 κ b a 2 κ ( − 1 ) a V a = ( − 1 ) κ V . (108) \sum_{a=0}^{\kappa}b_a^{2\kappa}(-1)^a\mathcal{V}_a=(-1)^\kappa\mathcal{V}. \tag*{(108)} a = 0 ∑ κ b a 2 κ ( − 1 ) a V a = ( − 1 ) κ V . (108)
Inserting (S49) and (S50) into (S46), we see that the coefficients of I q ( 0 ) I_q^{(0)} I q ( 0 ) , I q ( 1 ) I_q^{(1)} I q ( 1 ) ,... I q ( κ − 1 ) I_q^{(\kappa-1)} I q ( κ − 1 ) all vanish, and (S46) simplifies to
G ∘ [ ln Z r o t β ] = − 1 κ + 1 ∑ q = 0 ∞ I q ( κ ) . (109) \mathcal{G}\circ\left[\frac{\ln Z^{\mathrm{rot}}}{\beta}\right]=-\frac{1}{\kappa+1}\sum_{q=0}^{\infty}I_q^{(\kappa)}. \tag*{(109)} G ∘ [ β ln Z rot ] = − κ + 1 1 q = 0 ∑ ∞ I q ( κ ) . (109)
Expanding (S51) term by term, (and using that I q ( κ ) I_q^{(\kappa)} I q ( κ ) is homogeneous of degree ( q − κ ) (q-\kappa) ( q − κ ) in b μ 2 b_\mu^2 b μ 2 , μ = 0 … κ \mu=0\ldots\kappa μ = 0 … κ ), we arrive at (A3).
Relation to S 3 S_3 S 3 representation theory
We have demonstrated in the main text that if the ln Z r o t \ln Z^{\mathrm{rot}} ln Z rot of a CFT4 _4 4 is well described by a local thermal effective action, then it is constrained to obey Eq. (22) , which asserts that
S ∘ [ ln Z r o t β ] = 0 , (110) \mathcal{S}\circ\left[\frac{\ln Z^{\mathrm{rot}}}{\beta}\right]=0, \tag*{(110)} S ∘ [ β ln Z rot ] = 0 , (110)
where S \mathcal{S} S is defined in Eq. (21) . In this section we will view this condition (and resultant equations) from the lens of S 3 S_3 S 3 representation theory.
The permutation group S 3 S_3 S 3 acts on any function of ( b 0 2 , b 1 2 , b 2 2 ) (b_0^2,b_1^2,b_2^2) ( b 0 2 , b 1 2 , b 2 2 ) in the obvious way (by permuting the b i 2 b_i^2 b i 2 ). S 3 S_3 S 3 has three irreducible representations, namely the one dimensional 1 S \mathbf{1}_S 1 S totally symmetric and the 1 A \mathbf{1}_A 1 A totally antisymmetric representations, together with the two dimensional mixed representation 2 M \mathbf{2}_M 2 M . 26 A little thought will convince the reader that the quantities
P 1 S = 1 6 [ 1 + ( 01 ) + ( 02 ) + ( 12 ) + ( 012 ) + ( 021 ) ] , P_{1_S}=\frac{1}{6}[1+(01)+(02)+(12)+(012)+(021)], P 1 S = 6 1 [ 1 + ( 01 ) + ( 02 ) + ( 12 ) + ( 012 ) + ( 021 )] ,
P 1 A = 1 6 [ 1 − ( 01 ) − ( 02 ) − ( 12 ) + ( 012 ) + ( 021 ) ] , P_{1_A}=\frac{1}{6}[1-(01)-(02)-(12)+(012)+(021)], P 1 A = 6 1 [ 1 − ( 01 ) − ( 02 ) − ( 12 ) + ( 012 ) + ( 021 )] ,
P 2 M = 1 − P 1 S − P 1 A = 1 3 [ 2 − ( 012 ) − ( 021 ) ] . (111) P_{2_M}=1-P_{1_S}-P_{1_A}=\frac{1}{3}[2-(012)-(021)]. \tag*{(111)} P 2 M = 1 − P 1 S − P 1 A = 3 1 [ 2 − ( 012 ) − ( 021 )] . (111)
act as projectors onto the relevant representation spaces. In Eq. (111) we have used the following notation: 1 1 1 is the identity permutation, ( i j ) (ij) ( ij ) is the permutation that interchanges i i i and j j j , and ( i j k ) (ijk) ( ij k ) is the permutation that implements ( i → j → k → i ) (i\to j\to k\to i) ( i → j → k → i ) . The RHS of the first of Eq. (111) is one sixth the sum over all 6 permutations in S 3 S_3 S 3 , and so projects onto the totally symmetric representation. The RHS of the second of Eq. (111) is one sixth the signed sum over all 6 elements of the permutation group, and so projects onto the totally antisymmetric representation. The third line of Eq. (111) projects onto whatever is left after these two representations have been removed, and so projects onto the 2 M \mathbf{2}_M 2 M representation. In this notation Ω = ( 012 ) \Omega=(012) Ω = ( 012 ) and Ω 2 = ( 021 ) \Omega^2=(021) Ω 2 = ( 021 ) (see Eq. (6) for a definition of Ω \Omega Ω ) so that
S = 1 3 ( 1 + Ω + Ω 2 ) = P 1 S + P 1 A = 1 − P 2 M . (112) \mathcal{S}=\frac{1}{3}(1+\Omega+\Omega^2)=P_{1_S}+P_{1_A}=1-P_{2_M}. \tag*{(112)} S = 3 1 ( 1 + Ω + Ω 2 ) = P 1 S + P 1 A = 1 − P 2 M . (112)
In other words, S \mathcal{S} S is the projector onto the completely symmetric and completely antisymmetric subspaces, but projects out the mixed 2 M \mathbf{2}_M 2 M subspace. Consequently, Eq. (110) can be rewritten as
( P 1 S + P 1 A ) ∘ [ ln Z r o t β ] = 0. (113) (P_{1_S}+P_{1_A})\circ\left[\frac{\ln Z^{\mathrm{rot}}}{\beta}\right]=0. \tag*{(113)} ( P 1 S + P 1 A ) ∘ [ β ln Z rot ] = 0. (113)
Now the condition P 1 A ∘ [ ln Z r o t β ] = 0 P_{1_A}\circ\left[\frac{\ln Z^{\mathrm{rot}}}{\beta}\right]=0 P 1 A ∘ [ β l n Z rot ] = 0 follows trivially from the symmetry of ln Z r o t \ln Z^{\mathrm{rot}} ln Z rot under the interchange of b 1 2 b_1^2 b 1 2 and b 2 2 b_2^2 b 2 2 . The nontrivial condition in Eq. (113) is the assertion
P 1 S ∘ [ ln Z r o t β ] = 0 , ln Z r o t β ∈ 2 M . (114) P_{1_S}\circ\left[\frac{\ln Z^{\mathrm{rot}}}{\beta}\right]=0,\qquad\frac{\ln Z^{\mathrm{rot}}}{\beta}\in\mathbf{2}_M. \tag*{(114)} P 1 S ∘ [ β ln Z rot ] = 0 , β ln Z rot ∈ 2 M . (114)
Note also that while the 2 M \mathbf{2}_M 2 M representation is two dimensional, exactly one state in each representation is symmetric under the interchange of b 1 2 b_1^2 b 1 2 and b 2 2 b_2^2 b 2 2 (of course ln Z β \frac{\ln Z}{\beta} β l n Z enjoys this symmetry).
In order to make our discussion more quantitative, we now recall that ln Z r o t β \frac{\ln Z^{\mathrm{rot}}}{\beta} β l n Z rot can be written in the form Eq. (65) , where H ( y 0 , y 1 , y 2 ) H(y_0,y_1,y_2) H ( y 0 , y 1 , y 2 ) admits a power series expansion in its arguments. Let us recall (see e.g. [50 ] for a review) that the space of polynomials of arbitrary degree, of the three variables ( b 0 2 , b 1 2 , b 2 2 ) (b_0^2,b_1^2,b_2^2) ( b 0 2 , b 1 2 , b 2 2 ) , constitute a freely generated module. We sometimes use the following terminology: we call the degree of a monomial (in the three variables above) the level of the monomial. The generators of this module are the three S 3 S_3 S 3 invariant monomials E 1 E_1 E 1 , E 2 E_2 E 2 and E 3 E_3 E 3 (see Eq. (38) ). The module of all polynomials is not irreducible; it has four distinct submodules (each of which is freely generated, i.e. has no null states) and so has four distinct primaries. The first of these (at ‘level zero’) is monomial unity, in the 1 S \mathbf{1}_{S} 1 S representation. There are two primaries in the 2 M \mathbf{2}_{M} 2 M representation. The first of these, at level one, is given by linear combinations ( b 0 2 − b 1 2 ) (b_0^2-b_1^2) ( b 0 2 − b 1 2 ) , ( b 1 2 − b 2 2 ) (b_1^2-b_2^2) ( b 1 2 − b 2 2 ) , ( b 2 2 − b 0 2 ) (b_2^2-b_0^2) ( b 2 2 − b 0 2 ) (note these three functions span a two dimensional basis of functions). The second of these, at level two, is spanned by linear combinations of three functions ( b 0 2 b 2 2 − b 1 2 b 2 2 ) (b_0^2b_2^2-b_1^2b_2^2) ( b 0 2 b 2 2 − b 1 2 b 2 2 ) , ( b 1 2 b 0 2 − b 2 2 b 0 2 ) (b_1^2b_0^2-b_2^2b_0^2) ( b 1 2 b 0 2 − b 2 2 b 0 2 ) , ( b 2 2 b 1 2 − b 0 2 b 1 2 ) (b_2^2b_1^2-b_0^2b_1^2) ( b 2 2 b 1 2 − b 0 2 b 1 2 ) , once again a two dimensional space of functions. The last primary, at level three, lies in the 1 A \mathbf{1}_{A} 1 A representation, is given by V V V defined in Eq. (99) .
We can verify that the primaries listed above do indeed transform in the assigned representations by checking (for instance) that
P 1 S ∘ ( 1 ) = 1 , P 1 A ∘ ( 1 ) = P 2 M ∘ ( 1 ) = 0 , P 1 S ∘ ( b 1 2 − b 2 2 ) = P 1 A ∘ ( b 1 2 − b 2 2 ) = 0 , P 2 M ∘ ( b 1 2 − b 2 2 ) = b 1 2 − b 2 2 , P 1 S ∘ ( b 1 2 b 0 2 − b 2 2 b 0 2 ) = P 1 A ∘ ( b 1 2 b 0 2 − b 2 2 b 0 2 ) = 0 , P 2 M ∘ ( b 1 2 b 0 2 − b 2 2 b 0 2 ) = b 1 2 b 0 2 − b 2 2 b 0 2 , P 1 S ∘ ( P ) = 0 , P 1 A ∘ ( P ) = P , P 2 M ∘ ( P ) = 0. (115) \begin{aligned}
P_{\mathbf{1}_{S}}\circ(1)&=1,\quad P_{\mathbf{1}_{A}}\circ(1)=P_{\mathbf{2}_{M}}\circ(1)=0,\\
P_{\mathbf{1}_{S}}\circ(b_1^2-b_2^2)&=P_{\mathbf{1}_{A}}\circ(b_1^2-b_2^2)=0,\quad P_{\mathbf{2}_{M}}\circ(b_1^2-b_2^2)=b_1^2-b_2^2,\\
P_{\mathbf{1}_{S}}\circ(b_1^2b_0^2-b_2^2b_0^2)&=P_{\mathbf{1}_{A}}\circ(b_1^2b_0^2-b_2^2b_0^2)=0,\quad P_{\mathbf{2}_{M}}\circ(b_1^2b_0^2-b_2^2b_0^2)=b_1^2b_0^2-b_2^2b_0^2,\\
P_{\mathbf{1}_{S}}\circ(P)&=0,\quad P_{\mathbf{1}_{A}}\circ(P)=P,\quad P_{\mathbf{2}_{M}}\circ(P)=0. \tag*{(115)}
\end{aligned} P 1 S ∘ ( 1 ) P 1 S ∘ ( b 1 2 − b 2 2 ) P 1 S ∘ ( b 1 2 b 0 2 − b 2 2 b 0 2 ) P 1 S ∘ ( P ) = 1 , P 1 A ∘ ( 1 ) = P 2 M ∘ ( 1 ) = 0 , = P 1 A ∘ ( b 1 2 − b 2 2 ) = 0 , P 2 M ∘ ( b 1 2 − b 2 2 ) = b 1 2 − b 2 2 , = P 1 A ∘ ( b 1 2 b 0 2 − b 2 2 b 0 2 ) = 0 , P 2 M ∘ ( b 1 2 b 0 2 − b 2 2 b 0 2 ) = b 1 2 b 0 2 − b 2 2 b 0 2 , = 0 , P 1 A ∘ ( P ) = P , P 2 M ∘ ( P ) = 0. (115)
We will now count polynomials weighted by degree. Let z ( x ) z(x) z ( x ) denote the ‘trace’ Tr x L \operatorname{Tr}x^L Tr x L over the space of polynomials, where L L L denotes the level or degree of the monomials. Let z a l l ( x ) z_{\mathrm{all}}(x) z all ( x ) denote the partition function over all polynomials of our three variables. Let z 1 S ( x ) z_{\mathbf{1}_{S}}(x) z 1 S ( x ) , z 1 A ( x ) z_{\mathbf{1}_{A}}(x) z 1 A ( x ) and z 2 M ( x ) z_{\mathbf{2}_{M}}(x) z 2 M ( x ) , respectively, denote the partition functions over polynomials that transform in the corresponding representations. Then it follows from the construction of the free modules above that
z 1 S ( x ) = 1 ( 1 − x ) ( 1 − x 2 ) ( 1 − x 3 ) , z 1 A ( x ) = x 3 ( 1 − x ) ( 1 − x 2 ) ( 1 − x 3 ) , z 2 M ( x ) = 2 x + 2 x 2 ( 1 − x ) ( 1 − x 2 ) ( 1 − x 3 ) , z a l l ( x ) = 1 ( 1 − x ) 3 = z 1 S + z 1 A ( x ) + z 2 M ( x ) . (116) \begin{aligned}
z_{\mathbf{1}_{S}}(x)&=\frac{1}{(1-x)(1-x^2)(1-x^3)},\\
z_{\mathbf{1}_{A}}(x)&=\frac{x^3}{(1-x)(1-x^2)(1-x^3)},\\
z_{\mathbf{2}_{M}}(x)&=\frac{2x+2x^2}{(1-x)(1-x^2)(1-x^3)},\\
z_{\mathrm{all}}(x)&=\frac{1}{(1-x)^3}=z_{\mathbf{1}_{S}}+z_{\mathbf{1}_{A}}(x)+z_{\mathbf{2}_{M}}(x). \tag*{(116)}
\end{aligned} z 1 S ( x ) z 1 A ( x ) z 2 M ( x ) z all ( x ) = ( 1 − x ) ( 1 − x 2 ) ( 1 − x 3 ) 1 , = ( 1 − x ) ( 1 − x 2 ) ( 1 − x 3 ) x 3 , = ( 1 − x ) ( 1 − x 2 ) ( 1 − x 3 ) 2 x + 2 x 2 , = ( 1 − x ) 3 1 = z 1 S + z 1 A ( x ) + z 2 M ( x ) . (116)
We will now use the formulae Eq. (116) to count both the number of polynomials H ( b 0 2 , b 1 2 , b 2 2 ) H(b_0^2,b_1^2,b_2^2) H ( b 0 2 , b 1 2 , b 2 2 ) that are symmetric under 1 ↔ 2 1\leftrightarrow2 1 ↔ 2 , as well as the number of constraints on these polynomials.
Let z n a i v e ( x ) z_{\mathrm{naive}}(x) z naive ( x ) represent the partition function of polynomials symmetric under 1 ↔ 2 1\leftrightarrow2 1 ↔ 2 . Since every polynomial in the 1 S \mathbf{1}_{S} 1 S representation, exactly half the polynomials in the 2 M \mathbf{2}_{M} 2 M representation, and none of the polynomials in the 1 A \mathbf{1}_{A} 1 A representation enjoy this symmetry, it follows that
z n a i v e ( x ) = z 1 S ( x ) + 1 2 z 2 M ( x ) = 1 + x + x 2 ( 1 − x ) ( 1 − x 2 ) ( 1 − x 3 ) . (117) z_{\mathrm{naive}}(x)=z_{\mathbf{1}_{S}}(x)+\frac{1}{2}z_{\mathbf{2}_{M}}(x)=\frac{1+x+x^2}{(1-x)(1-x^2)(1-x^3)}. \tag*{(117)} z naive ( x ) = z 1 S ( x ) + 2 1 z 2 M ( x ) = ( 1 − x ) ( 1 − x 2 ) ( 1 − x 3 ) 1 + x + x 2 . (117)
in agreement with (D2).
Of course the count Eq. (117) does not account for the fact that the polynomials in the function H H H are constrained to obey the equation Eq. (66) . In order to understand the S 3 S_3 S 3 representation content of (S7), we rederive this equation as follows. We use ln Z r o t β = P H ( b 1 2 − b 2 2 ) 2 π 2 \frac{\ln Z^{\mathrm{rot}}}{\beta}=\frac{P H(b_1^2-b_2^2)}{2\pi^2} β l n Z rot = 2 π 2 P H ( b 1 2 − b 2 2 ) to obtain
P 1 S ∘ [ ln Z r o t β ] = 1 2 π 2 P 1 S ∘ [ P ( b 1 2 − b 2 2 ) H ] = P 2 π 2 P 1 A ∘ [ ( b 1 2 − b 2 2 ) H ] . (118) P_{\mathbf{1}_{S}}\circ\left[\frac{\ln Z^{\mathrm{rot}}}{\beta}\right]=\frac{1}{2\pi^2}P_{\mathbf{1}_{S}}\circ\left[P(b_1^2-b_2^2)H\right]=\frac{P}{2\pi^2}P_{\mathbf{1}_{A}}\circ\left[(b_1^2-b_2^2)H\right]. \tag*{(118)} P 1 S ∘ [ β ln Z rot ] = 2 π 2 1 P 1 S ∘ [ P ( b 1 2 − b 2 2 ) H ] = 2 π 2 P P 1 A ∘ [ ( b 1 2 − b 2 2 ) H ] . (118)
Note that pulling out the completely antisymmetric object P P P has turned the projector onto the symmetric representation in the middle of Eq. (118) into a projector onto the antisymmetric representation in the last of (S60). Inserting Eq. (118) into the first of Eq. (114) yields the equation
P 1 A ∘ [ ( b 1 2 − b 2 2 ) H ] = 0. (119) P_{\mathbf{1}_{A}}\circ\left[(b_1^2-b_2^2)H\right]=0. \tag*{(119)} P 1 A ∘ [ ( b 1 2 − b 2 2 ) H ] = 0. (119)
But Eq. (119) is simply a rewriting of the equation Eq. (66) , as may be verified by expanding out the projector on the LHS of Eq. (119) and using the 1 ↔ 2 1\leftrightarrow2 1 ↔ 2 symmetry of H H H .
We see that the LHS of Eq. (66) lies in the 1 A \mathbf{1}_{A} 1 A representation. A little thought will convince the reader that any polynomial 1 A \mathbf{1}_{A} 1 A representation can be obtained from the constraint equation (LHS of Eq. (66) ) for a suitable choice of the function H H H . We thus conclude that the constraint equation Eq. (66) on the degree L L L part of H H H is in one to one correspondence with polynomials of degree L + 1 L+1 L + 1 in the 1 A \mathbf{1}_{A} 1 A representation. The partition function over such polynomials equals z 1 A ( x ) x \frac{z_{1A}(x)}{x} x z 1 A ( x ) (the division by x x x accounts for the shift in level by unity, i.e. the ‘one’ in ‘L + 1 L+1 L + 1 ’), in perfect agreement with (5). The partition function over polynomials H H H subject to the constraint Eq. (66) is thus given by z a c c ( x ) z_{\mathrm{acc}}(x) z acc ( x )
z a c c ( x ) = z 1 S ( x ) + 1 2 z 2 M ( x ) − z 1 A ( x ) x = 1 + x ( 1 − x ) ( 1 − x 2 ) ( 1 − x 3 ) (120) z_{\mathrm{acc}}(x)=z_{1S}(x)+\frac{1}{2}z_{2M}(x)-\frac{z_{1A}(x)}{x}=\frac{1+x}{(1-x)(1-x^{2})(1-x^{3})} \tag*{(120)} z acc ( x ) = z 1 S ( x ) + 2 1 z 2 M ( x ) − x z 1 A ( x ) = ( 1 − x ) ( 1 − x 2 ) ( 1 − x 3 ) 1 + x (120)
in perfect agreement with Eq. (59) .
Polynomial nature of I \mathcal{I} I in 2 κ 2\kappa 2 κ dimensions, κ ≥ 2 \kappa\ge2 κ ≥ 2
In this section we demonstrate that I \mathcal{I} I , the local integrand of the thermal effective action, takes the form of a polynomial (more precisely a power series expansion) in a suitable set of variables. The result of this subsection will be a key input into our derivation, presented in subsequent subsections, of the analytic structure of the expansion (3) and the central equation (7) for CFTs in arbitrary even dimensions.
The discussion of this subsection can be viewed as a generalization (also an independent rederivation) of (19) to arbitrary even dimensions. As in the rest of this paper, we work with CP even theories whose partition function is well described by a local thermal effective action.
Throughout this Appendix we work in the embedding space, R 2 κ , 2 \mathbb{R}^{2\kappa,2} R 2 κ , 2 , (see e.g. Appendix B of [51 ] for a review). The manifold S 2 κ − 1 × R S^{2\kappa-1}\times\mathbb{R} S 2 κ − 1 × R (up to Weyl transformations) on which our CFT lives is isomorphic to the space of null rays, N \mathcal{N} N , of this embedding spacetime (we work with the Lorentzian continuation of the Euclidean set up in the main text). Points on this spacetime are parameterized by N P N^{P} N P (P = − 1 , 0 , 1 … 2 κ P=-1,0,1\ldots2\kappa P = − 1 , 0 , 1 … 2 κ ) that obey N 2 = 0 N^{2}=0 N 2 = 0 . N N N dependent scaling of the null vector N N N change the Weyl frame in our boundary spacetime. In this section we choose to work in the Weyl frame relevant to the computation of the partition function ln Z r o t \ln Z^{\mathrm{rot}} ln Z rot (see Appendix A of [6 ] ). We can reach this Weyl gauge starting with the metric g μ ν g_{\mu\nu} g μν in any Weyl frame, and then performing the Weyl rescaling that sets the metric equal to
g μ ν v 2 (121) \frac{g_{\mu\nu}}{v^{2}} \tag*{(121)} v 2 g μν (121)
where v 2 v^{2} v 2 is computed in the metric g μ ν g_{\mu\nu} g μν .27
The vector v v v in embedding-space variables and the Cayley–Hamilton relation
Recall that the vector v v v is a conformal Killing vector. Conformal Killing vectors are in one-to-one correspondence with the generators of S O ( 2 κ , 2 ) SO(2\kappa,2) S O ( 2 κ , 2 ) , and so with dimension ( 2 κ + 2 ) × ( 2 κ + 2 ) (2\kappa+2)\times(2\kappa+2) ( 2 κ + 2 ) × ( 2 κ + 2 ) matrices A Q P A^{P}_{Q} A Q P s.t.28
η A T = − A η , ⟹ ( A η ) T = − A η (122) \eta A^{T}=-A\eta,\qquad\Longrightarrow\qquad(A\eta)^{T}=-A\eta \tag*{(122)} η A T = − A η , ⟹ ( A η ) T = − A η (122)
where η = η − 1 \eta=\eta^{-1} η = η − 1 is the diagonal metric on R 2 κ , 2 R^{2\kappa,2} R 2 κ , 2 . We see that the matrix A η A\eta A η (which has both upper indices) is antisymmetric; i.e. the matrix A A A is antisymmetric with respect to the embedding-space metric.
Now let us suppose that λ \lambda λ is an eigenvalue of the matrix A A A . This implies that
det ( A − λ I ) = 0 ⟹ det ( A η − λ η ) = 0 ⟹ det ( ( A η ) T − λ η T ) = 0 ⟹ det ( − A η − λ η ) = 0 ⟹ det ( A + λ I ) = 0 (123) \begin{aligned}
\det(A-\lambda I)&=0\\
\Longrightarrow\det(A\eta-\lambda\eta)&=0\\
\Longrightarrow\det((A\eta)^{T}-\lambda\eta^{T})&=0\\
\Longrightarrow\det(-A\eta-\lambda\eta)&=0\\
\Longrightarrow\det(A+\lambda I)&=0 \tag*{(123)}
\end{aligned} det ( A − λ I ) ⟹ det ( A η − λ η ) ⟹ det (( A η ) T − λ η T ) ⟹ det ( − A η − λ η ) ⟹ det ( A + λ I ) = 0 = 0 = 0 = 0 = 0 (123)
so that − λ -\lambda − λ is also an eigenvalue of A A A . It follows, therefore, that all eigenvalues of the matrix B B B defined by
B : = − A 2 . (124) B:=-A^{2}. \tag*{(124)} B := − A 2 . (124)
have degeneracy two (B B B , like A A A , has index structure B Q P B^{P}_{Q} B Q P ). It follows that B B B has κ + 1 \kappa+1 κ + 1 distinct eigenvalues, each with multiplicity two. We denote them by
( c 0 , c 1 , … , c κ ) . (125) (c_0,c_1,\ldots,c_\kappa). \tag*{(125)} ( c 0 , c 1 , … , c κ ) . (125)
In order to understand the physical meaning of c i c_i c i , consider the standard form vector ( v L ) μ (v_L)_\mu ( v L ) μ , which, in Lorentzian space, takes the form
v L = i v E = β ( ∂ t + ω 1 ∂ ϕ 1 + ⋯ + ω κ ∂ ϕ κ ) (126) v_L=iv_E=\beta\left(\partial_t+\omega_1\partial_{\phi_1}+\cdots+\omega_\kappa\partial_{\phi_\kappa}\right) \tag*{(126)} v L = i v E = β ( ∂ t + ω 1 ∂ ϕ 1 + ⋯ + ω κ ∂ ϕ κ ) (126)
where “L” denotes Lorentzian and “E” denotes Euclidean. This CKV clearly corresponds to a block diagonal matrix A A A , whose 2 × 2 2\times2 2 × 2 blocks are
\begin{pmatrix}0&\beta\\-\beta&0\end{pmatrix},
\qquad\text{and}\qquad
\begin{pmatrix}0&\beta\omega_i\\-\beta\omega_i&0\end{pmatrix}
\quad\text{for }i=1,2,\ldots,\kappa. \tag*{(127)}\end{pmatrix}
Computing the eigenvalues of B = − A 2 B=-A^2 B = − A 2 , we identify
( c 0 , c 1 , … , c κ ) = ( b 0 2 , b 1 2 , … , b κ 2 ) = ( β 2 , β 2 ω 1 2 , … , β 2 ω κ 2 ) . (128) (c_0,c_1,\ldots,c_\kappa)=(b_0^2,b_1^2,\ldots,b_\kappa^2)=(\beta^2,\beta^2\omega_1^2,\ldots,\beta^2\omega_\kappa^2). \tag*{(128)} ( c 0 , c 1 , … , c κ ) = ( b 0 2 , b 1 2 , … , b κ 2 ) = ( β 2 , β 2 ω 1 2 , … , β 2 ω κ 2 ) . (128)
Below we will also often use the completely symmetric polynomials E r E_r E r defined in Eq. (38) ; or equivalently via
Q ( t ) : = ∏ i = 0 κ ( t − c i ) = t κ + 1 − E 1 t κ + E 2 t κ − 1 − ⋯ + ( − 1 ) κ + 1 E κ + 1 . (129) Q(t):=\prod_{i=0}^{\kappa}(t-c_i)=t^{\kappa+1}-E_1t^\kappa+E_2t^{\kappa-1}-\cdots+(-1)^{\kappa+1}E_{\kappa+1}. \tag*{(129)} Q ( t ) := i = 0 ∏ κ ( t − c i ) = t κ + 1 − E 1 t κ + E 2 t κ − 1 − ⋯ + ( − 1 ) κ + 1 E κ + 1 . (129)
We emphasize that E r E_r E r depend only on the unordered ‘compactification data’ and are therefore S κ + 1 S_{\kappa+1} S κ + 1 invariant.
Fixing the Weyl gauge
It is now a simple matter to fix Weyl ‘gauge’ as in Eq. (121) . Recall that N N N is a null ray and so obeys
N 2 = 0. (130) N^2=0. \tag*{(130)} N 2 = 0. (130)
In the Weyl gauge (S63) it follows from definitions that v 2 = 1 v^2=1 v 2 = 1 . A little thought will convince the reader that v 2 v^2 v 2 is given, in embedding space notation, by
v 2 = − ( A N ) 2 = N ⋅ A 2 N = − N ⋅ B N . (131) v^2=-(AN)^2=N\cdot A^2N=-N\cdot BN. \tag*{(131)} v 2 = − ( A N ) 2 = N ⋅ A 2 N = − N ⋅ B N . (131)
(the minus sign converts the Lorentzian norm of A N AN A N into the Euclidean v 2 v^2 v 2 ; compare (S97)). Thus the Weyl gauge Eq. (121) is implemented by rescaling all null rays to ensure that
N ⋅ B N = − 1 (132) N\cdot BN=-1 \tag*{(132)} N ⋅ B N = − 1 (132)
(S74) implements our choice of Weyl gauge.
Coordinates in embedding space
Below, we will make frequent use of the position-dependent quantities
m j : = − N ⋅ B j N , m 0 = 0 , m 1 = 1. (133) m_j:=-N\cdot B^jN,\qquad m_0=0,\qquad m_1=1. \tag*{(133)} m j := − N ⋅ B j N , m 0 = 0 , m 1 = 1. (133)
Recall that m j m_j m j depend both on the compactification data, as well as on the location on the sphere. In contrast, the quantities E r E_r E r above, are position independent, but depend only on the compactification data. We will now explain that each of the m j m_j m j , (j = 2 … ∞ j=2\ldots\infty j = 2 … ∞ ) and each tr ( B j ) \operatorname{tr}(B^j) tr ( B j ) (j = 1 … ∞ j=1\ldots\infty j = 1 … ∞ ) can be rewritten as a polynomial in the ‘generators’
E 1 , … , E κ + 1 , m 2 , … , m κ . (134) E_1,\ldots,E_{\kappa+1},\qquad m_2,\ldots,m_\kappa. \tag*{(134)} E 1 , … , E κ + 1 , m 2 , … , m κ . (134)
The simple argument for this result goes as follows. As every matrix obeys its characteristic equation, it follows that
Q ( B ) = B κ + 1 − E 1 B κ + E 2 B κ − 1 − ⋯ + ( − 1 ) κ + 1 E κ + 1 = 0. (135) Q(B)=B^{\kappa+1}-E_1B^\kappa+E_2B^{\kappa-1}-\cdots+(-1)^{\kappa+1}E_{\kappa+1}=0 . \tag*{(135)} Q ( B ) = B κ + 1 − E 1 B κ + E 2 B κ − 1 − ⋯ + ( − 1 ) κ + 1 E κ + 1 = 0. (135)
Multiplying Eq. (135) by B r B^r B r and placing the result between two N N N 's gives
m r + κ + 1 = E 1 m r + κ − E 2 m r + κ − 1 + ⋯ + ( − 1 ) κ E κ + 1 m r . (136) m_{r+\kappa+1}=E_1m_{r+\kappa}-E_2m_{r+\kappa-1}+\cdots+(-1)^\kappa E_{\kappa+1}m_r . \tag*{(136)} m r + κ + 1 = E 1 m r + κ − E 2 m r + κ − 1 + ⋯ + ( − 1 ) κ E κ + 1 m r . (136)
Using the same equation on every m s m_s m s with s ≥ κ + 1 s\geq\kappa+1 s ≥ κ + 1 term on the RHS of Eq. (136) , and repeatedly iterating this process, we conclude that every m j m_j m j with j > κ j>\kappa j > κ can be rewritten as a polynomial in the generators listed in (S76). In a similar manner, it follows that all of the Tr B j = 2 ∑ a c a j \operatorname{Tr} B^j=2\sum_a c_a^j Tr B j = 2 ∑ a c a j can be rewritten in terms of the E r E_r E r .
The m j m_j m j defined above, constitute a set of κ − 1 \kappa-1 κ − 1 coordinates on ( S 2 κ − 1 × R ) / G v (S^{2\kappa-1}\times R)/G_v ( S 2 κ − 1 × R ) / G v ; where G v G_v G v is the subgroup of S O ( 2 κ , 2 ) SO(2\kappa,2) S O ( 2 κ , 2 ) that leaves v v v invariant. When v v v takes the standard form (S68), the G v G_v G v is the κ + 1 \kappa+1 κ + 1 dimensional abelian subgroup consisting of rotations (translations) in each of the ϕ i \phi_i ϕ i and t t t . Consequently, the ( κ − 1 ) (\kappa-1) ( κ − 1 ) quantities m j m_j m j , together with t t t and ϕ i \phi_i ϕ i , constitute a full set of coordinates on S 2 κ − 1 × R S^{2\kappa-1}\times R S 2 κ − 1 × R . Indeed, as we will see below, κ − 1 \kappa-1 κ − 1 m j m_j m j can be written as functions of the κ − 1 \kappa-1 κ − 1 direction cosines on S 2 κ − 1 S^{2\kappa-1} S 2 κ − 1 . As the coordinates m j m_j m j have been defined in a completely S O ( d , 2 ) SO(d,2) S O ( d , 2 ) invariant manner, however, they will prove more useful than the direction cosines themselves, in our analysis below.
The projector
The metric of S 2 κ − 1 × R S^{2\kappa-1}\times R S 2 κ − 1 × R , in our particular choice of Weyl frame, is given by the metric on R 2 κ , 2 R^{2\kappa,2} R 2 κ , 2 restricted to the codimension-two submanifold defined by (S72) and (S74). Consider any point N 0 N_0 N 0 on this manifold. Let N = N 0 + δ N N=N_0+\delta N N = N 0 + δ N . Working to first order in δ N \delta N δ N , the equations (S72) and (S74) reduce, at first nontrivial order in δ N \delta N δ N , to
δ N ⋅ N 0 = 0 , δ N ⋅ B N 0 = 0. (137) \delta N\cdot N_0=0,\qquad\delta N\cdot BN_0=0 . \tag*{(137)} δ N ⋅ N 0 = 0 , δ N ⋅ B N 0 = 0. (137)
(S79), viewed as two constraints on the vectors δ N \delta N δ N , defines the tangent space of our submanifold around the point N 0 N_0 N 0 . We will now construct Π \Pi Π , the projector onto the 2 κ 2\kappa 2 κ dimensional tangent space described above. The simplicity (polynomial nature) of this projector will play a key role in the remaining analysis below.
Consider a general n n n dimensional linear vector space. Consider a collection of m m m vectors v ( a ) μ v^\mu_{(a)} v ( a ) μ (a = 1 … m a=1\ldots m a = 1 … m ) in this space. Let G a b G_{ab} G ab denote the m × m m\times m m × m matrix of inner products of these vectors, and let G a b G^{ab} G ab denote the inverse of G a b G_{ab} G ab . Then the projector onto the orthogonal complement of the space spanned by v ( a ) v_{(a)} v ( a ) is given by
Π ν μ = δ ν μ − G a b v ( a ) μ v ( b ) ν . (138) \Pi^\mu_{\ \nu}=\delta^\mu_{\ \nu}-G^{ab}v^\mu_{(a)}v_{(b)\nu}. \tag*{(138)} Π ν μ = δ ν μ − G ab v ( a ) μ v ( b ) ν . (138)
Note, in particular, that independent rescalings of v ( a ) v_{(a)} v ( a ) leave this projector unchanged.
We can now apply the general formula (S80) to obtain the projector onto the tangent space of a general point N N N on the submanifold described by (S72) and (S74). In this case m = 2 m=2 m = 2 , and the two vectors v ( a ) v_{(a)} v ( a ) are N N N and B N BN B N respectively. The matrix of inner products of these two vectors is given by
G a b = ( N 2 N ⋅ B N B N ⋅ N ( B N ) 2 ) = ( 0 − 1 − 1 − m 2 ) . (139) G_{ab}=
\begin{pmatrix}
N^2 & N\cdot BN\\
BN\cdot N & (BN)^2
\end{pmatrix}
=
\begin{pmatrix}
0 & -1\\
-1 & -m_2
\end{pmatrix}. \tag*{(139)} G ab = ( N 2 B N ⋅ N N ⋅ B N ( B N ) 2 ) = ( 0 − 1 − 1 − m 2 ) . (139)
A key simplification is that the determinant of this matrix is − 1 -1 − 1 . For this reason, the inverse of this matrix contains no denominator depending on the position on the sphere, and is given by
G a b = ( m 2 − 1 − 1 0 ) . (140) G^{ab}=
\begin{pmatrix}
m_2 & -1\\
-1 & 0
\end{pmatrix}. \tag*{(140)} G ab = ( m 2 − 1 − 1 0 ) . (140)
It follows from (S80) that projector onto our tangent space is given by
Π P Q = δ P Q − m 2 N Q N P + N Q ( B N ) P + ( B N ) Q N P \Pi^Q_{\ P}=\delta^Q_{\ P}-m_2N^QN_P+N^Q(BN)_P+(BN)^QN_P Π P Q = δ P Q − m 2 N Q N P + N Q ( B N ) P + ( B N ) Q N P
⟹ Π V = V − m 2 N ( N ⋅ V ) + N ( B N ⋅ V ) + B N ( N ⋅ V ) . (141) \Longrightarrow\quad\Pi V=V-m_2N(N\cdot V)+N(BN\cdot V)+BN(N\cdot V) . \tag*{(141)} ⟹ Π V = V − m 2 N ( N ⋅ V ) + N ( B N ⋅ V ) + B N ( N ⋅ V ) . (141)
Covariant derivatives preserve the polynomial nature
Whenever a manifold can be viewed as a submanifold of a flat space, the covariant derivative (of any tensor on the submanifold) is obtained by taking the ordinary derivative of that tensor (along the relevant tangent derivatives of the manifold), and projecting the result of this computation back onto the tangent space of the manifold.
In the current context, our boundary spacetime consists of the codimension two submanifold of R 2 κ , 2 \mathbb{R}^{2\kappa,2} R 2 κ , 2 defined by (S72) and (S74), and the projector onto tangent space is given by Eq. (141) . Applying the prescription spelled out in the previous paragraph, we conclude that
∇ ˉ U V = Π D U V , (142) \bar{\nabla}_{U}V = \Pi D_{U}V \,, \tag*{(142)} ∇ ˉ U V = Π D U V , (142)
where D U D_U D U is the ordinary flat space derivative dotted with the tangent vector U U U (which we assume to lie in the tangent space of our manifold).
Now recall that A A A (the generator dual to v v v ) and B = − A 2 B=-A^2 B = − A 2 are both constant matrices in embedding-space. Because the ordinary derivatives of these constant matrices vanishes, it follows that
D U A = 0 , D U B = 0 . (143) D_U A = 0 \,, \qquad D_U B = 0 \,. \tag*{(143)} D U A = 0 , D U B = 0 . (143)
Moreover, the covariant derivative of the vector field N A N^A N A is given by
( D U N ) P = Π Q P U M ∂ M N Q = Π Q P U Q = U P , ⟹ D U N = U . (144) (D_U N)^P = \Pi^P_Q U^M \partial_M N^Q = \Pi^P_Q U^Q = U^P \,, \qquad\Longrightarrow\quad D_U N = U \,. \tag*{(144)} ( D U N ) P = Π Q P U M ∂ M N Q = Π Q P U Q = U P , ⟹ D U N = U . (144)
It follows that differentiating a polynomial expression in A , B , N A,B,N A , B , N gives another polynomial expression before projection. The key equation (S83) then shows us that the projection itself introduces no denominator.
Since the m j m_j m j are themselves polynomials of N N N and B B B , the discussion above implies that covariant derivatives of m j m_j m j are themselves polynomials in m j m_j m j and E r E_r E r . We can also directly verify this conclusion as follows. It follows immediately from the definition of the m j m_j m j in (S75) that
∇ ˉ P m j = Π P Q ∂ Q m j = − 2 Π P Q ( B j ) Q R N R = − 2 ( B j N ) P − 2 ( m 2 m j − m j + 1 ) N P + 2 m j ( B N ) P . (145) \bar{\nabla}_P m_j = \Pi_P^Q \partial_Q m_j = -2\Pi_P^Q (B^j)_{QR}N^R = -2(B^jN)_P - 2(m_2m_j-m_{j+1})N_P + 2m_j(BN)_P \,. \tag*{(145)} ∇ ˉ P m j = Π P Q ∂ Q m j = − 2 Π P Q ( B j ) QR N R = − 2 ( B j N ) P − 2 ( m 2 m j − m j + 1 ) N P + 2 m j ( B N ) P . (145)
The RHS is polynomial, as expected. Repeated derivatives of (S87), followed by repeated use of (S83), therefore remain polynomial as well.
The Riemann Tensor
A similar conclusion also holds for all curvature invariants. As our submanifold is embedded in flat space, its Riemann tensor is given by the Gauss–Codazzi equations
R P Q R S = G a b ( K P R ( a ) K Q S ( b ) − K P S ( a ) K Q R ( b ) ) , (146) R_{PQRS}=G^{ab}\left(K^{(a)}_{PR}K^{(b)}_{QS}-K^{(a)}_{PS}K^{(b)}_{QR}\right) \,, \tag*{(146)} R P QR S = G ab ( K P R ( a ) K QS ( b ) − K P S ( a ) K QR ( b ) ) , (146)
where G a b G^{ab} G ab is given in (S82). Here K μ ν ( a ) K^{(a)}_{\mu\nu} K μν ( a ) are the extrinsic curvatures defined by
K P Q ( a ) : = Π P P ′ Π Q Q ′ D P ′ n Q ′ ( a ) . (147) K^{(a)}_{PQ}:=\Pi_P^{P'}\Pi_Q^{Q'}D_{P'}n^{(a)}_{Q'} \,. \tag*{(147)} K P Q ( a ) := Π P P ′ Π Q Q ′ D P ′ n Q ′ ( a ) . (147)
As around (S81) we choose our two normal vectors n ( a ) n^{(a)} n ( a ) to be N P N^P N P and ( B N ) P (BN)^P ( B N ) P . The two extrinsic curvatures are thus
K P Q ( 1 ) = Π P P ′ Π Q Q ′ D P ′ N Q ′ = Π P P ′ Π P ′ Q = Π P Q , K^{(1)}_{PQ}=\Pi_P^{P'}\Pi_Q^{Q'}D_{P'}N_{Q'}=\Pi_P^{P'}\Pi_{P'Q}=\Pi_{PQ} \,, K P Q ( 1 ) = Π P P ′ Π Q Q ′ D P ′ N Q ′ = Π P P ′ Π P ′ Q = Π P Q ,
K P Q ( 2 ) = Π P P ′ Π Q Q ′ D P ′ ( B N ) Q ′ = Π P P ′ Π Q Q ′ B P ′ Q ′ : = M P Q , (148) K^{(2)}_{PQ}=\Pi_P^{P'}\Pi_Q^{Q'}D_{P'}(BN)_{Q'}=\Pi_P^{P'}\Pi_Q^{Q'}B_{P'Q'}:=M_{PQ} \,, \tag*{(148)} K P Q ( 2 ) = Π P P ′ Π Q Q ′ D P ′ ( B N ) Q ′ = Π P P ′ Π Q Q ′ B P ′ Q ′ := M P Q , (148)
where we have used D P N Q = η P Q D_PN_Q=\eta_{PQ} D P N Q = η P Q . Putting (S90) into (S88), the Riemann tensor is
R P Q R S = m 2 ( Π P R Π Q S − Π P S Π Q R ) − M P R Π Q S − Π P R M Q S + M P S Π Q R + Π P S M Q R . (149) R_{PQRS}=m_2\left(\Pi_{PR}\Pi_{QS}-\Pi_{PS}\Pi_{QR}\right)-M_{PR}\Pi_{QS}-\Pi_{PR}M_{QS}+M_{PS}\Pi_{QR}+\Pi_{PS}M_{QR} \,. \tag*{(149)} R P QR S = m 2 ( Π P R Π QS − Π P S Π QR ) − M P R Π QS − Π P R M QS + M P S Π QR + Π P S M QR . (149)
The following identities can be obtained using (S90) and (S83)
M P P = M P Q η Q P = Tr Π B = Tr B − m 2 , M^P_P=M_{PQ}\eta^{QP}=\operatorname{Tr}\Pi B=\operatorname{Tr}B-m_2 \,, M P P = M P Q η QP = Tr Π B = Tr B − m 2 ,
M P Q M P Q = Tr [ Π B Π B ] = Tr B 2 + m 2 2 − 2 m 3 . (150) M_{PQ}M^{PQ}=\operatorname{Tr}\left[\Pi B\Pi B\right]=\operatorname{Tr}B^2+m_2^2-2m_3 \,. \tag*{(150)} M P Q M P Q = Tr [ Π B Π B ] = Tr B 2 + m 2 2 − 2 m 3 . (150)
Hence, these scalars are also polynomials. Using (S91) and (S92), we get
R P Q = ( d m 2 − Tr B ) Π P Q − ( d − 2 ) M P Q , R_{PQ}=(d\,m_2-\operatorname{Tr}B)\Pi_{PQ}-(d-2)M_{PQ} \,, R P Q = ( d m 2 − Tr B ) Π P Q − ( d − 2 ) M P Q ,
R = ( d − 1 ) [ ( d + 2 ) m 2 − 2 Tr B ] . (151) R=(d-1)\left[(d+2)m_2-2\operatorname{Tr}B\right] \,. \tag*{(151)} R = ( d − 1 ) [ ( d + 2 ) m 2 − 2 Tr B ] . (151)
Sample curvature invariants
The other curvature invariants are
R P Q R P Q = d ( d m 2 − Tr B ) 2 − 2 ( d − 2 ) ( d m 2 − Tr B ) ( Tr B − m 2 ) + ( d − 2 ) 2 [ Tr ( B 2 ) + m 2 2 − 2 m 3 ] (152) R_{PQ}R^{PQ}=d\left(d m_{2}-\operatorname{Tr} B\right)^{2}-2(d-2)\left(d m_{2}-\operatorname{Tr} B\right)\left(\operatorname{Tr} B-m_{2}\right)+(d-2)^{2}\left[\operatorname{Tr}\left(B^{2}\right)+m_{2}^{2}-2m_{3}\right] \tag*{(152)} R P Q R P Q = d ( d m 2 − Tr B ) 2 − 2 ( d − 2 ) ( d m 2 − Tr B ) ( Tr B − m 2 ) + ( d − 2 ) 2 [ Tr ( B 2 ) + m 2 2 − 2 m 3 ] (152)
R P Q R S R P Q R S = 2 d ( d − 1 ) m 2 2 − 8 ( d − 1 ) m 2 ( Tr B − m 2 ) + 4 ( Tr B − m 2 ) 2 + 4 ( d − 2 ) [ Tr ( B 2 ) + m 2 2 − 2 m 3 ] . (153) R_{PQRS}R^{PQRS}=2d(d-1)m_{2}^{2}-8(d-1)m_{2}\left(\operatorname{Tr} B-m_{2}\right)+4\left(\operatorname{Tr} B-m_{2}\right)^{2}+4(d-2)\left[\operatorname{Tr}\left(B^{2}\right)+m_{2}^{2}-2m_{3}\right]. \tag*{(153)} R P QR S R P QR S = 2 d ( d − 1 ) m 2 2 − 8 ( d − 1 ) m 2 ( Tr B − m 2 ) + 4 ( Tr B − m 2 ) 2 + 4 ( d − 2 ) [ Tr ( B 2 ) + m 2 2 − 2 m 3 ] . (153)
One can easily see that all these scalars are polynomials. Derivatives of curvature are also polynomial as the derivatives act only on m i m_i m i 's since B B B is spacetime independent. From (S87),
( ∇ ˉ m j ) ⋅ ( ∇ ˉ m k ) = 4 [ − m j + k + m j m k + 1 + m k m j + 1 − m 2 m j m k ] . (154) \left(\bar{\nabla}m_j\right)\cdot\left(\bar{\nabla}m_k\right)=4\left[-m_{j+k}+m_jm_{k+1}+m_km_{j+1}-m_2m_jm_k\right]. \tag*{(154)} ( ∇ ˉ m j ) ⋅ ( ∇ ˉ m k ) = 4 [ − m j + k + m j m k + 1 + m k m j + 1 − m 2 m j m k ] . (154)
Since Tr B \operatorname{Tr} B Tr B is independent of position, the second of (S93) gives, for instance,
( ∇ ˉ R ) 2 = 4 ( d − 1 ) 2 ( d + 2 ) 2 [ − m 4 + 2 m 2 m 3 − m 2 3 ] . (155) \left(\bar{\nabla}R\right)^2=4(d-1)^2(d+2)^2\left[-m_4+2m_2m_3-m_2^3\right]. \tag*{(155)} ( ∇ ˉ R ) 2 = 4 ( d − 1 ) 2 ( d + 2 ) 2 [ − m 4 + 2 m 2 m 3 − m 2 3 ] . (155)
When m 4 m_4 m 4 is not part of the set (S76), it is eliminated using (S78). The same procedure applies to any finite number of covariant derivatives.
In the metric induced on the codimension two manifold (S79), the unit thermal vector is
u : = A N , u 2 = − N A 2 N = N B N = − 1 , (156) u:=AN,\qquad u^2=-NA^2N=NB N=-1, \tag*{(156)} u := A N , u 2 = − N A 2 N = N B N = − 1 , (156)
(u 2 = − 1 u^2=-1 u 2 = − 1 makes sense because we are in Lorentzian space; this continues to u 2 = 1 u^2=1 u 2 = 1 in Euclidean space).
The projection orthogonal to u u u therefore also introduces no denominator. Upon completely contracting a finite local scalar, every term reduces to products of traces and contractions involving two N N N 's,
Tr A 2 j = Tr ( − B ) j , N ⋅ A 2 j N = ( − 1 ) j + 1 m j . (157) \operatorname{Tr}A^{2j}=\operatorname{Tr}(-B)^j,\qquad N\cdot A^{2j}N=(-1)^{j+1}m_j. \tag*{(157)} Tr A 2 j = Tr ( − B ) j , N ⋅ A 2 j N = ( − 1 ) j + 1 m j . (157)
Odd traces and N ⋅ A 2 j + 1 N N\cdot A^{2j+1}N N ⋅ A 2 j + 1 N vanish because A A A is antisymmetric. Combining these statements with (S78) and the fact that Tr B j = 2 ∑ i c i j \operatorname{Tr}B^j=2\sum_i c_i^j Tr B j = 2 ∑ i c i j is a polynomial in the symmetric invariants E r E_r E r , we conclude that at every fixed order in the local thermal effective action
I = I ( E 1 , … , E κ + 1 ; m 2 , … , m κ ) (158) \mathcal{I}=\mathcal{I}(E_1,\ldots,E_{\kappa+1};m_2,\ldots,m_\kappa) \tag*{(158)} I = I ( E 1 , … , E κ + 1 ; m 2 , … , m κ ) (158)
is a polynomial. Its coefficients are theory-dependent Wilson coefficients and do not depend on the compactification data. In d = 4 d=4 d = 4 there is only one position-dependent variable m 2 m_2 m 2 . In the next subsection we will demonstrate that m 2 m_2 m 2 is related to the variable z z z (defined in (15) and used extensively in the main text) via
z = E 1 − m 2 . (159) z=E_1-m_2. \tag*{(159)} z = E 1 − m 2 . (159)
Thus the fact that I \mathcal{I} I , in the four dimensional case, is polynomial, both in the variables z z z and in the variables b i 2 b_i^2 b i 2 (see (18) ) follows directly from the general discussion of this subsection.
The integral over S 2 κ − 1 S^{2\kappa-1} S 2 κ − 1 for κ ≥ 2 \kappa\geq2 κ ≥ 2
In the previous subsection we have demonstrated that the integrand, I \mathcal{I} I , of the thermal effective action is a polynomial in the variables m i m_i m i and E r E_r E r (see e.g. (E)). In this subsection we study the integral over such I \mathcal{I} I over the rotating sphere and, in particular, demonstrate that its analytic structure takes the form presented in the first of (3) . The final formulae of this subsection will also form the starting point for our derivation of (6) in the next subsection.
Below, we will find it convenient to switch between several distinct coordinates for S 2 κ − 1 S^{2\kappa-1} S 2 κ − 1 . We first pause to define and introduce each of these coordinate systems.
Direction cosines
One familiar set of coordinates on S 2 κ − 1 S^{2\kappa-1} S 2 κ − 1 consists of the κ \kappa κ angles ϕ i \phi_i ϕ i (dual to the κ \kappa κ angular momenta J i J_i J i , together with the κ \kappa κ ‘direction cosines’ ℓ i \ell_i ℓ i which are constrained to sum to unity. More concretely, these coordinates are defined as follows. Let us view our unit sphere as embedded in C κ \mathbb{C}^{\kappa} C κ (and centered around its origin). Then S 2 κ − 1 ⊂ C κ S^{2\kappa-1} \subset\mathbb{C}^{\kappa} S 2 κ − 1 ⊂ C κ is given by the locus of points
z i = ℓ i e i ϕ i , ℓ i ≥ 0 , ∑ i = 1 κ ℓ i = 1. (160) z_i = \sqrt{\ell_i}e^{i\phi_i}, \qquad\ell_i \ge0, \qquad\sum_{i=1}^{\kappa} \ell_i = 1 . \tag*{(160)} z i = ℓ i e i ϕ i , ℓ i ≥ 0 , i = 1 ∑ κ ℓ i = 1. (160)
In these coordinates, the round sphere metric times R R R is given by
d s 2 = d τ 2 + ∑ m = 1 κ ( d ℓ m 2 4 ℓ m + ℓ m d ϕ m 2 ) . (161) ds^2 = d\tau^2 + \sum_{m=1}^{\kappa} \left(\frac{d\ell_m^2}{4\ell_m} + \ell_m d\phi_m^2\right) . \tag*{(161)} d s 2 = d τ 2 + m = 1 ∑ κ ( 4 ℓ m d ℓ m 2 + ℓ m d ϕ m 2 ) . (161)
In the coordinates (S102), the norm of the vector v v v (see (13) ) is given by
v 2 = β 2 − ∑ i = 1 κ ℓ i β 2 ω i 2 = β 2 ( ∑ i = 1 κ ℓ i ) − ∑ i = 1 κ ℓ i β 2 ω i 2 = ∑ i = 1 κ ( c 0 − c i ) ℓ i . (162) v^2 = \beta^2 - \sum_{i=1}^{\kappa} \ell_i\beta^2\omega_i^2 = \beta^2\left(\sum_{i=1}^{\kappa}\ell_i\right) - \sum_{i=1}^{\kappa}\ell_i\beta^2\omega_i^2 = \sum_{i=1}^{\kappa}(c_0-c_i)\ell_i . \tag*{(162)} v 2 = β 2 − i = 1 ∑ κ ℓ i β 2 ω i 2 = β 2 ( i = 1 ∑ κ ℓ i ) − i = 1 ∑ κ ℓ i β 2 ω i 2 = i = 1 ∑ κ ( c 0 − c i ) ℓ i . (162)
In these coordinates, the thermal effective action is given in terms of the density I \mathcal{I} I by
ln Z r o t β = ( 2 π ) κ 2 κ − 1 ∫ ℓ i ≥ 0 , ∑ i ℓ i = 1 d κ − 1 ℓ ( v 2 ) κ I ( E , m ) , (163) \frac{\ln Z^{\mathrm{rot}}}{\beta} = \frac{(2\pi)^{\kappa}}{2^{\kappa-1}}\int_{\substack{\ell_i\ge0,\\ \sum_i\ell_i=1}}\frac{d^{\kappa-1}\ell}{(v^2)^{\kappa}}\mathcal{I}(E,m) , \tag*{(163)} β ln Z rot = 2 κ − 1 ( 2 π ) κ ∫ ℓ i ≥ 0 , ∑ i ℓ i = 1 ( v 2 ) κ d κ − 1 ℓ I ( E , m ) , (163)
(the factor of ( 2 π ) κ (2\pi)^{\kappa} ( 2 π ) κ comes from performing the integrals over the κ \kappa κ angles ϕ i \phi_i ϕ i and 2 κ − 1 2^{\kappa-1} 2 κ − 1 in the denominator comes from g \sqrt{g} g ).
We can visualize the integration region in ℓ i \ell_i ℓ i as living on the plane ∑ j ℓ j = 1 \sum_j\ell_j=1 ∑ j ℓ j = 1 embedded in the κ \kappa κ dimensional space, whose axes are ℓ i \ell_i ℓ i (i = 1 … κ i=1\ldots\kappa i = 1 … κ ). The boundary of the integration region is given by the intersection of this plane with the κ \kappa κ codimension one surfaces ℓ i = 0 \ell_i=0 ℓ i = 0 , (i = 1 … κ i=1\ldots\kappa i = 1 … κ ). These are the surfaces on which the angles ϕ i \phi_i ϕ i shrink in the full geometry (this shrinking happens in a smooth way, like at the origin of 2d polar coordinates).
The coordinates λ i \lambda_i λ i
For reasons that will soon become clear, we will sometimes find it convenient to change coordinates from ℓ i \ell_i ℓ i to λ i \lambda_i λ i where
λ i : = ( c 0 − c i ) ℓ i v 2 , λ i ≥ 0 , ∑ i = 1 κ λ i = 1. (164) \lambda_i := \frac{(c_0-c_i)\ell_i}{v^2}, \qquad\lambda_i \ge0, \qquad\sum_{i=1}^{\kappa}\lambda_i = 1 . \tag*{(164)} λ i := v 2 ( c 0 − c i ) ℓ i , λ i ≥ 0 , i = 1 ∑ κ λ i = 1. (164)
This coordinate change is easily inverted to find ℓ i \ell_i ℓ i in terms of λ i \lambda_i λ i via
ℓ i = λ i / ( c 0 − c i ) ∑ j λ j / ( c 0 − c j ) . (165) \ell_i = \frac{\lambda_i/(c_0-c_i)}{\sum_j\lambda_j/(c_0-c_j)} . \tag*{(165)} ℓ i = ∑ j λ j / ( c 0 − c j ) λ i / ( c 0 − c i ) . (165)
Inserting (S106) allows us to express v 2 v^2 v 2 as a function of the λ i \lambda_i λ i , yielding
v 2 = ( ∑ j λ j c 0 − c j ) − 1 . (166) v^2 = \left(\sum_j\frac{\lambda_j}{c_0-c_j}\right)^{-1} . \tag*{(166)} v 2 = ( j ∑ c 0 − c j λ j ) − 1 . (166)
The Jacobian of the variable change from ℓ i \ell_i ℓ i to λ i \lambda_i λ i is easily determined from (S106). After some algebra we find
d κ − 1 ℓ ( v 2 ) κ = d κ − 1 λ ∏ i = 1 κ ( c 0 − c i ) . (167) \frac{d^{\kappa-1}\ell}{(v^2)^{\kappa}} = \frac{d^{\kappa-1}\lambda}{\prod_{i=1}^{\kappa}(c_0-c_i)} . \tag*{(167)} ( v 2 ) κ d κ − 1 ℓ = ∏ i = 1 κ ( c 0 − c i ) d κ − 1 λ . (167)
The key point here is that the λ i \lambda_i λ i (unlike ℓ i \ell_i ℓ i ) are ‘flat’ coordinates; all the position dependence in the denominator of (S108) has disappeared.
The integration domain for the λ i \lambda_i λ i can be visualized in the same way as for the ℓ i \ell_i ℓ i above. As in that case, the ϕ i \phi_i ϕ i circles shrink to zero on the codimension one surfaces λ i = 0 \lambda_i=0 λ i = 0 .
The integration domain in the λ i \lambda_i λ i can be restated as follows. Working in the Cartesian space ( λ 1 , λ 2 … λ κ ) (\lambda_1,\lambda_2\ldots\lambda_\kappa) ( λ 1 , λ 2 … λ κ ) , consider the κ \kappa κ distinct unit vectors e 1 = ( 1 , 0 , … , 0 ) \mathbf{e}_1=(1,0,\ldots,0) e 1 = ( 1 , 0 , … , 0 ) , e 2 = ( 0 , 1 , 0 , … , 0 ) , … e κ = ( 0 , 0 , 0 , … , 1 ) \mathbf{e}_2=(0,1,0,\ldots,0),\ldots\mathbf{e}_\kappa=(0,0,0,\ldots,1) e 2 = ( 0 , 1 , 0 , … , 0 ) , … e κ = ( 0 , 0 , 0 , … , 1 ) . The integration domain is given by
∑ j λ j e j , λ i ≥ 0 , ∑ j = 1 κ λ j = 1. (168) \sum_j\lambda_j\mathbf{e}_j,\quad\lambda_i\geq0,\quad\sum_{j=1}^{\kappa}\lambda_j=1. \tag*{(168)} j ∑ λ j e j , λ i ≥ 0 , j = 1 ∑ κ λ j = 1. (168)
However (S109) is the definition of a polytope built out of the κ \kappa κ vectors e 1 … e κ \mathbf{e}_1\ldots\mathbf{e}_\kappa e 1 … e κ . We conclude that the integration domain in λ i \lambda_i λ i is a polytope built out of the vectors described above.
mi as coordinates
As we have already explained in the previous subsection, the quantities m i m_i m i , defined in (S75), can also be used as a set of coordinates for S 2 κ − 1 S^{2\kappa-1} S 2 κ − 1 . This can be made quantitative by rewriting the definition of m i m_i m i in a ‘Weyl’ gauge invariant form
m j = N ⋅ B j N N ⋅ B N (169) m_j=\frac{N\cdot B^jN}{N\cdot BN} \tag*{(169)} m j = N ⋅ B N N ⋅ B j N (169)
(S110) is the Weyl invariant generalization of (S75) because
We can now use the Weyl invariant definition (S110), to compute m j m_j m j directly in the ‘round sphere’ Weyl frame adopted in this subsection. In the round sphere Weyl frame, the null vector N N N is given, in terms of angles and direction cosines by
N = ( cos t , sin t , l 1 cos ϕ 1 , l 1 sin ϕ 1 , l 2 cos ϕ 2 , l 2 sin ϕ 2 … l κ cos ϕ κ , l κ sin ϕ κ ) , (170) N=\left(\cos t,\sin t,\sqrt{l_1}\cos\phi_1,\sqrt{l_1}\sin\phi_1,\sqrt{l_2}\cos\phi_2,\sqrt{l_2}\sin\phi_2\ldots\sqrt{l_\kappa}\cos\phi_\kappa,\sqrt{l_\kappa}\sin\phi_\kappa\right), \tag*{(170)} N = ( cos t , sin t , l 1 cos ϕ 1 , l 1 sin ϕ 1 , l 2 cos ϕ 2 , l 2 sin ϕ 2 … l κ cos ϕ κ , l κ sin ϕ κ ) , (170)
(where t t t is global Lorentzian time; note that the first two coordinates in (170) are timelike, while the remaining are spacelike). In the same basis, the matrix A A A takes the block diagonal form (S69), and B = − A 2 B=-A^2 B = − A 2 . A simple computation then yields
m j = c 0 j − ∑ i c i j l i v 2 , (171) m_j=\frac{c_0^j-\sum_i c_i^j l_i}{v^2}, \tag*{(171)} m j = v 2 c 0 j − ∑ i c i j l i , (171)
29
and hence
m j = ∑ i = 1 κ λ i c 0 j − c i j c 0 − c i = ∑ i = 1 κ λ i ( c 0 j − 1 + c 0 j − 2 c i + ⋯ + c i j − 1 ) . (172) \begin{aligned}
m_j&=\sum_{i=1}^{\kappa}\lambda_i\frac{c_0^j-c_i^j}{c_0-c_i}\\
&=\sum_{i=1}^{\kappa}\lambda_i\left(c_0^{j-1}+c_0^{j-2}c_i+\cdots+c_i^{j-1}\right). \tag*{(172)}
\end{aligned} m j = i = 1 ∑ κ λ i c 0 − c i c 0 j − c i j = i = 1 ∑ κ λ i ( c 0 j − 1 + c 0 j − 2 c i + ⋯ + c i j − 1 ) . (172)
Note that the apparent denominator in the first line cancels. It follows that m j m_j m j is a linear function of the λ i \lambda_i λ i , with coefficients that are polynomials in the c a c_a c a .
Integration measure in m i m_i m i coordinates
The integration measure over the m a m_a m a may be worked out as follows. (S108) can be rewritten as
1 ∏ j = 1 κ ( c 0 − c j ) ∫ d λ 1 ∧ d λ 2 … d λ κ δ ( λ 1 + λ 2 + … λ κ − 1 ) . (173) \frac{1}{\prod_{j=1}^{\kappa}(c_0-c_j)}\int d\lambda_1\wedge d\lambda_2\ldots d\lambda_\kappa\delta(\lambda_1+\lambda_2+\ldots\lambda_\kappa-1). \tag*{(173)} ∏ j = 1 κ ( c 0 − c j ) 1 ∫ d λ 1 ∧ d λ 2 … d λ κ δ ( λ 1 + λ 2 + … λ κ − 1 ) . (173)
Using the delta function to integrate out (say) λ 1 \lambda_1 λ 1 , we can rewrite the first of (S113) as
m j = c 0 j − c 1 j c 0 − c 1 + ∑ i = 2 κ λ i ( c 0 j − c i j c 0 − c i − c 0 j − c 1 j c 0 − c 1 ) , (174) m_j=\frac{c_0^j-c_1^j}{c_0-c_1}+\sum_{i=2}^{\kappa}\lambda_i\left(\frac{c_0^j-c_i^j}{c_0-c_i}-\frac{c_0^j-c_1^j}{c_0-c_1}\right), \tag*{(174)} m j = c 0 − c 1 c 0 j − c 1 j + i = 2 ∑ κ λ i ( c 0 − c i c 0 j − c i j − c 0 − c 1 c 0 j − c 1 j ) , (174)
so that (S114) can be rewritten as
1 det A ~ ∏ j = 1 κ ( c 0 − c j ) d m 2 ∧ d m 3 … d m κ , (175) \frac{1}{\det\widetilde{A}\prod_{j=1}^{\kappa}(c_0-c_j)}dm_2\wedge dm_3\ldots dm_\kappa, \tag*{(175)} det A ∏ j = 1 κ ( c 0 − c j ) 1 d m 2 ∧ d m 3 … d m κ , (175)
where the ( κ − 1 ) × ( κ − 1 ) (\kappa-1)\times(\kappa-1) ( κ − 1 ) × ( κ − 1 ) matrix A ~ \widetilde{A} A (see (S115)) equals
A ~ j i = B j i − B j 1 , ( i , j = 2 … κ ) \widetilde{A}_{ji}=B_{ji}-B_{j1},\qquad(i,j=2\ldots\kappa) A j i = B j i − B j 1 , ( i , j = 2 … κ )
B j i = c 0 j − c i j c 0 − c i , B j 1 = c 0 j − c 1 j c 0 − c 1 . (176) B_{ji}=\frac{c_0^j-c_i^j}{c_0-c_i},\qquad B_{j1}=\frac{c_0^j-c_1^j}{c_0-c_1}. \tag*{(176)} B j i = c 0 − c i c 0 j − c i j , B j 1 = c 0 − c 1 c 0 j − c 1 j . (176)
As defined, B B B is a ( κ − 1 ) × κ (\kappa-1)\times\kappa ( κ − 1 ) × κ matrix. We can enhance it to a κ × κ \kappa\times\kappa κ × κ matrix by adding a row of ones, i.e by defining
B ^ = ( 1 1 ⋯ 1 B 2 , 1 B 2 , 2 ⋯ B 2 , κ ⋮ ⋮ ⋮ B κ , 1 B κ , 2 ⋯ B κ , κ ) . (177) \widehat{B}=
\begin{pmatrix}
1 & 1 & \cdots& 1\\
B_{2,1} & B_{2,2} & \cdots& B_{2,\kappa}\\
\vdots& \vdots& & \vdots\\
B_{\kappa,1} & B_{\kappa,2} & \cdots& B_{\kappa,\kappa}
\end{pmatrix}. \tag*{(177)} B = 1 B 2 , 1 ⋮ B κ , 1 1 B 2 , 2 ⋮ B κ , 2 ⋯ ⋯ ⋯ 1 B 2 , κ ⋮ B κ , κ . (177)
By subtracting the first column of B ^ \widehat{B} B from each of its last κ − 1 \kappa-1 κ − 1 columns, we see that
det B ^ = det ( 1 0 0 ⋯ 0 B 2 , 1 A ~ 2 , 2 A ~ 2 , 3 ⋯ A ~ 2 , κ ⋮ ⋮ ⋮ B κ , 1 A ~ κ , 2 A ~ κ , 3 ⋯ A ~ κ , κ ) . (178) \det\widehat{B}=\det\begin{pmatrix}
1 & 0 & 0 & \cdots& 0\\
B_{2,1} & \widetilde{A}_{2,2} & \widetilde{A}_{2,3} & \cdots& \widetilde{A}_{2,\kappa}\\
\vdots& \vdots& & & \vdots\\
B_{\kappa,1} & \widetilde{A}_{\kappa,2} & \widetilde{A}_{\kappa,3} & \cdots& \widetilde{A}_{\kappa,\kappa}
\end{pmatrix}. \tag*{(178)} det B = det 1 B 2 , 1 ⋮ B κ , 1 0 A 2 , 2 ⋮ A κ , 2 0 A 2 , 3 A κ , 3 ⋯ ⋯ ⋯ 0 A 2 , κ ⋮ A κ , κ . (178)
We conclude that
det B ^ = det A ~ . (179) \det\widehat{B}=\det\widetilde{A}. \tag*{(179)} det B = det A . (179)
Now the determinant of B ^ \widehat{B} B is clearly of degree 1 + 2 + … κ − 1 = κ ( κ − 1 ) 2 1+2+\ldots\kappa-1=\frac{\kappa(\kappa-1)}{2} 1 + 2 + … κ − 1 = 2 κ ( κ − 1 ) in the variables c 0 , c 1 … c κ c_0,c_1\ldots c_\kappa c 0 , c 1 … c κ . Moreover this determinant vanishes whenever c i = c j c_i=c_j c i = c j for any i , j ∈ 1 … κ i,j\in1\ldots\kappa i , j ∈ 1 … κ . It follows that the determinant has ∏ i < j ( c i − c j ) \prod_{i<j}(c_i-c_j) ∏ i < j ( c i − c j ) as a factor. As this factor already has the required degree, it follows that det B ^ \det\widehat{B} det B is, in fact, independent of c 0 c_0 c 0 . The proportionality constant can be obtained by examining the coefficient of a particular term, and we find
det B ^ = ∏ 1 ≤ i < j ≤ κ ( c j − c i ) . (180) \det\widehat{B}=\prod_{1\leq i<j\leq\kappa}(c_j-c_i). \tag*{(180)} det B = 1 ≤ i < j ≤ κ ∏ ( c j − c i ) . (180)
Inserting (S121) and (S120) into (S116) we have
1 det A ~ ∏ j = 1 κ ( c 0 − c j ) d m 2 ∧ d m 3 … d m κ = ( − 1 ) κ ∏ 0 ≤ i < j ≤ κ ( c j − c i ) d m 2 ∧ d m 3 … d m κ . (181) \frac{1}{\det\widetilde{A}\prod_{j=1}^{\kappa}(c_0-c_j)}dm_2\wedge dm_3\ldots dm_\kappa
=
\frac{(-1)^\kappa}{\prod_{0\leq i<j\leq\kappa}(c_j-c_i)}dm_2\wedge dm_3\ldots dm_\kappa. \tag*{(181)} det A ∏ j = 1 κ ( c 0 − c j ) 1 d m 2 ∧ d m 3 … d m κ = ∏ 0 ≤ i < j ≤ κ ( c j − c i ) ( − 1 ) κ d m 2 ∧ d m 3 … d m κ . (181)
Defining V \mathcal{V} V (the arbitrary dimensional generalization of the four dimensional Vandermonde 2 π 2 P \frac{2\pi^2}{P} P 2 π 2 ) by
V : = ∏ 0 ≤ i < j ≤ κ ( c j − c i ) , (182) \mathcal{V} := \prod_{0\leq i<j\leq\kappa}(c_j-c_i), \tag*{(182)} V := 0 ≤ i < j ≤ κ ∏ ( c j − c i ) , (182)
(note that V \mathcal{V} V defined in (S123) is the same quantity as V \mathcal{V} V defined in (S41)) and adding in the factors of ( 2 π ) κ (2\pi)^\kappa ( 2 π ) κ from the angle integrals we obtain our final integration measure
( − 1 ) κ 2 π κ V d m 2 ∧ d m 3 … d m κ . (183) (-1)^\kappa\frac{2\pi^\kappa}{\mathcal{V}}\,dm_2\wedge dm_3\ldots dm_\kappa. \tag*{(183)} ( − 1 ) κ V 2 π κ d m 2 ∧ d m 3 … d m κ . (183)
The integration range in m i m_i m i coordinates
As the m j m_j m j are linear functions of the λ i \lambda_i λ i , it follows that the integration domain in the m j m_j m j continues to be given by a polytope. The polytope has κ \kappa κ distinct ‘vertices’ (i.e. defining vectors). The V 0 ( a ) V_0^{(a)} V 0 ( a ) th vertex (a = 1 … κ a=1\ldots\kappa a = 1 … κ ) of this polytope is given by the vector
( m 2 , m 3 … m κ ) = ( ( V 0 ( a ) ) 2 , ( V 0 ( a ) ) 3 , … ( V 0 ( a ) ) κ ) , (184) (m_2,m_3\ldots m_\kappa)=\left(\left(V_0^{(a)}\right)_2,\left(V_0^{(a)}\right)_3,\ldots\left(V_0^{(a)}\right)_\kappa\right), \tag*{(184)} ( m 2 , m 3 … m κ ) = ( ( V 0 ( a ) ) 2 , ( V 0 ( a ) ) 3 , … ( V 0 ( a ) ) κ ) , (184)
where (see (S113))
( V 0 ( b ) ) j = c 0 j − c b j c 0 − c b . (185) \left(V_0^{(b)}\right)_j=\frac{c_0^j-c_b^j}{c_0-c_b}. \tag*{(185)} ( V 0 ( b ) ) j = c 0 − c b c 0 j − c b j . (185)
For use below, we define the quantities
s j ( a , b ) : = c a j − c b j c a − c b = c a j − 1 + c a j − 2 c b + ⋯ + c b j − 1 , b ≠ a , (186) s_j(a,b):=\frac{c_a^j-c_b^j}{c_a-c_b}=c_a^{j-1}+c_a^{j-2}c_b+\cdots+c_b^{j-1},\qquad b\ne a, \tag*{(186)} s j ( a , b ) := c a − c b c a j − c b j = c a j − 1 + c a j − 2 c b + ⋯ + c b j − 1 , b = a , (186)
in terms of which the vertices of our polytope can be rewritten as
( V 0 ( b ) ) j = s j ( 0 , b ) . (187) \left(V_0^{(b)}\right)_j=s_j(0,b). \tag*{(187)} ( V 0 ( b ) ) j = s j ( 0 , b ) . (187)
Consequently, the integration region in the variables m j m_j m j is given by the polytope built out of the vertex vectors (S128). More explicitly, the integration region, D 0 D_0 D 0 , is given by
D 0 : m j = ∑ b = 1 κ λ b s j ( 0 , b ) , ∑ b = 1 κ λ b = 1 , λ b ≥ 0 , (188) D_0:\qquad m_j=\sum_{b=1}^{\kappa}\lambda_b s_j(0,b),\qquad\sum_{b=1}^{\kappa}\lambda_b=1,\qquad\lambda_b\geq0, \tag*{(188)} D 0 : m j = b = 1 ∑ κ λ b s j ( 0 , b ) , b = 1 ∑ κ λ b = 1 , λ b ≥ 0 , (188)
with an orientation we will describe in more detail below.
The analytic structure of Z r o t Z^{\mathrm{rot}} Z rot
It follows from (S129) that
( ln Z r o t β ) = ( − 1 ) κ 2 π κ V ∫ D 0 d m 2 ∧ d m 3 … ∧ d m κ I ( E , m ( a ) ) (189) \left(\frac{\ln Z^{\mathrm{rot}}}{\beta}\right)=\frac{(-1)^\kappa2\pi^\kappa}{\mathcal{V}}\int_{D_0}dm_2\wedge dm_3\ldots\wedge dm_\kappa\ \mathcal{I}\left(E,m^{(a)}\right) \tag*{(189)} ( β ln Z rot ) = V ( − 1 ) κ 2 π κ ∫ D 0 d m 2 ∧ d m 3 … ∧ d m κ I ( E , m ( a ) ) (189)
(S130) is the generalization (to arbitrary dimension) of the four dimensional formula (18).
In the previous subsection we have demonstrated that the integrand in (S130) is a polynomial in the E r E_r E r and m i m_i m i . As the integration limits in (S130) are all polynomials in c a c_a c a (see the second of (S113)), it follows that the result of the integral in (S130) is a polynomial in E r E_r E r and c a c_a c a , and so is a polynomial in c b c_b c b , b = 0 … κ b=0\ldots\kappa b = 0 … κ .
We can actually say more. As we have explained above, at generic values of c a c_a c a , the integration region D 0 D_0 D 0 is a κ − 1 \kappa-1 κ − 1 dimensional polytope constructed out of the κ \kappa κ vectors V ( a ) V^{(a)} V ( a ) , a = 1 … κ a=1\ldots\kappa a = 1 … κ . In the limit that c a = c b c_a=c_b c a = c b (for any two particular values of a a a and b b b ), however, the vectors V ( a ) V^{(a)} V ( a ) and V ( b ) V^{(b)} V ( b ) tend to each other, and the polytope tends to a κ − 2 \kappa-2 κ − 2 dimensional surface. As the integral of a κ − 1 \kappa-1 κ − 1 form over a κ − 2 \kappa-2 κ − 2 dimensional surface always vanishes, it follows that
∫ D 0 d m 2 ∧ d m 3 … ∧ d m κ I ( E , m ( a ) ) \int_{\mathcal{D}_0} dm_2 \wedge dm_3 \ldots\wedge dm_\kappa\,\mathcal{I}\left(E,m^{(a)}\right) ∫ D 0 d m 2 ∧ d m 3 … ∧ d m κ I ( E , m ( a ) )
vanishes (and, in fact, generically develops a simple zero) in the limit c a → c b c^a \to c^b c a → c b . Since this holds for every pair ( a , b ) (a,b) ( a , b ) , we conclude that
∫ D 0 d m 2 ∧ d m 3 … ∧ d m κ I ( E , m ( a ) ) = ∏ 1 ≤ a < b ≤ κ ( c a − c b ) × Q (190) \int_{\mathcal{D}_0} dm_2 \wedge dm_3 \ldots\wedge dm_\kappa\,\mathcal{I}\left(E,m^{(a)}\right)=\prod_{1\leq a<b\leq\kappa}(c_a-c_b)\times Q \tag*{(190)} ∫ D 0 d m 2 ∧ d m 3 … ∧ d m κ I ( E , m ( a ) ) = 1 ≤ a < b ≤ κ ∏ ( c a − c b ) × Q (190)
where Q Q Q is a polynomial (more generally, admits a power series expansion) in c a c_a c a . Plugging (S131) into (S130), and using the definition of V \mathcal{V} V , we conclude that
( ln Z r o t β ) ∝ 1 ∏ b = 1 κ ( c 0 − c b ) × Q (191) \left(\frac{\ln Z^{\mathrm{rot}}}{\beta}\right)\propto\frac{1}{\prod_{b=1}^{\kappa}(c_0-c_b)}\times Q \tag*{(191)} ( β ln Z rot ) ∝ ∏ b = 1 κ ( c 0 − c b ) 1 × Q (191)
demonstrating that ln Z r o t \ln Z^{\mathrm{rot}} ln Z rot has the analytic structure expressed in the second of (3). Our proof applies in every even dimension.
Derivation of our central equation in every even dimension
In this subsection we demonstrate that (7) holds for any CP invariant CFT2 κ _{2\kappa} 2 κ for κ ≥ 2 \kappa\geq2 κ ≥ 2 (whose partition function is well defined by a thermal effective action), generalizing the d = 4 d=4 d = 4 (κ = 2 \kappa=2 κ = 2 ) derivation presented in the main text. The starting point for our derivation is (S130), derived in the previous subsection.
Action of permutations
We now study the action of the Z κ + 1 \mathbb{Z}_{\kappa+1} Z κ + 1 generator Ω \Omega Ω (defined in (6)) on ln Z r o t β \frac{\ln Z^{\mathrm{rot}}}{\beta} β l n Z rot . Recall from (S42) that Ω a ∘ V = ( − 1 ) κ a V \Omega^a\circ\mathcal{V}=(-1)^{\kappa a}\mathcal{V} Ω a ∘ V = ( − 1 ) κa V . Recall also that I \mathcal{I} I is function of E r E_r E r and m i m_i m i , both of which are S κ + 1 S_{\kappa+1} S κ + 1 (hence Z κ + 1 \mathbb{Z}_{\kappa+1} Z κ + 1 ) invariant. We conclude that Ω a ∘ I = I \Omega^a\circ\mathcal{I}=\mathcal{I} Ω a ∘ I = I . Finally, Ω a \Omega^a Ω a maps the integration range D 0 \mathcal{D}_0 D 0 to D a \mathcal{D}_a D a , where D a \mathcal{D}_a D a is the polytope built out of the κ \kappa κ distinct vectors V a ( b ) V_a^{(b)} V a ( b ) , b = 0 , … , κ b=0,\ldots,\kappa b = 0 , … , κ , b ≠ a b\ne a b = a , where
( V a ( b ) ) j = c a j − c b j c a − c b = s j ( a , b ) . (192) \left(V_a^{(b)}\right)_j=\frac{c_a^j-c_b^j}{c_a-c_b}=s_j(a,b). \tag*{(192)} ( V a ( b ) ) j = c a − c b c a j − c b j = s j ( a , b ) . (192)
Note that V a ( b ) = V b ( a ) V_a^{(b)}=V_b^{(a)} V a ( b ) = V b ( a ) . Below we will sometimes also use the notation
p a b = V a ( b ) = V b ( a ) . (193) p_{ab}=V_a^{(b)}=V_b^{(a)}. \tag*{(193)} p ab = V a ( b ) = V b ( a ) . (193)
In order to properly define the domain of integration described above, we need to specify both the polytope as well as its orientation. There is a natural way of associating an orientation of the polytope with an ordering of its defining vectors; given the ordered vector set ( v 1 , v 2 … v n + 1 ) (v^1,v^2\ldots v^{n+1}) ( v 1 , v 2 … v n + 1 ) , we declare that the n n n tuples of vectors ( ( v 2 − v 1 ) , ( v 3 − v 1 ) , … , ( v n + 1 − v 1 ) ) \left((v^2-v^1),(v^3-v^1),\ldots,(v^{n+1}-v^1)\right) ( ( v 2 − v 1 ) , ( v 3 − v 1 ) , … , ( v n + 1 − v 1 ) ) are positively/ negatively oriented, depending on whether the n × n n\times n n × n determinant of ordered column vectors is positive or negative. We can, more carefully, specify the integration range D 0 \mathcal{D}_0 D 0 by specifying that the vectors (S133) that form the edges of the polytope are ordered as ( 1 , 2 , 3 , … κ ) (1,2,3,\ldots\kappa) ( 1 , 2 , 3 , … κ ) . The permutation operator Ω a \Omega^a Ω a maps this choice of ordering to the polytope specified by the vectors (S133) ordered as
( V a ( a + 1 ) , V a ( a + 2 ) , … , V a κ , V a ( 0 ) , … , V a ( a − 1 ) ) . (194) \left(V_a^{(a+1)},V_a^{(a+2)},\ldots,V_a^\kappa,V_a^{(0)},\ldots,V_a^{(a-1)}\right). \tag*{(194)} ( V a ( a + 1 ) , V a ( a + 2 ) , … , V a κ , V a ( 0 ) , … , V a ( a − 1 ) ) . (194)
However, we choose to define the polytope D a \mathcal{D}_a D a with V ( a ) V^{(a)} V ( a ) ordered in increasing order. Moving to this ordering from that used in (S135) requires us to first pull V ( 0 ) V^{(0)} V ( 0 ) to the left of all vectors, then pull V ( 1 ) V^{(1)} V ( 1 ) to the left of all vectors and so on. The net sign induced by this process equals ( − 1 ) ( κ − a ) a (-1)^{(\kappa-a)a} ( − 1 ) ( κ − a ) a . Including the sign from the action of Ω a \Omega^a Ω a on V \mathcal{V} V , we get ( − 1 ) a 2 = ( − 1 ) a (-1)^{a^2}=(-1)^a ( − 1 ) a 2 = ( − 1 ) a . With this ‘increasing’ definition of D a \mathcal{D}_a D a , we conclude that
Ω a ∘ ( ln Z r o t β ) = 2 π κ ( − 1 ) κ − a V ∫ D a d m 2 ∧ d m 3 … ∧ d m κ I ( E , m ( a ) ) (195) \Omega^a \circ\left(\frac{\ln Z^{\mathrm{rot}}}{\beta}\right)=\frac{2\pi^\kappa(-1)^{\kappa-a}}{\mathcal{V}}\int_{\mathcal{D}_a}dm_2\wedge dm_3\ldots\wedge dm_\kappa\,\mathcal{I}\left(E,m^{(a)}\right) \tag*{(195)} Ω a ∘ ( β ln Z rot ) = V 2 π κ ( − 1 ) κ − a ∫ D a d m 2 ∧ d m 3 … ∧ d m κ I ( E , m ( a ) ) (195)
where the factor of ( − 1 ) κ (-1)^\kappa ( − 1 ) κ is carried over from (S130). In what follows, it will be useful to rewrite (S136) in the slightly more compact form
( ln Z r o t β ) a = 2 π κ V ( − 1 ) κ − a ∫ D a Υ (196) \left(\frac{\ln Z^{\mathrm{rot}}}{\beta}\right)_a=\frac{2\pi^\kappa}{\mathcal{V}}(-1)^{\kappa-a}\int_{\mathcal{D}_a}\Upsilon \tag*{(196)} ( β ln Z rot ) a = V 2 π κ ( − 1 ) κ − a ∫ D a Υ (196)
where the κ − 1 \kappa-1 κ − 1 form Υ \Upsilon Υ is defined by
Υ = d m 2 ∧ d m 3 … ∧ d m κ I . (197) \Upsilon=dm_2\wedge dm_3\ldots\wedge dm_\kappa\,\mathcal{I}. \tag*{(197)} Υ = d m 2 ∧ d m 3 … ∧ d m κ I . (197)
d=4
In the simple special case of four dimensions, we have already seen in (17) that the contour for the original integral, the contour for the action of Ω \Omega Ω , and the contour for the action of Ω 2 \Omega^2 Ω 2 , respectively, are given by the three oriented intervals
[ c 1 , c 2 ] , [ c 2 , c 0 ] , [ c 0 , c 1 ] . (198) [c_1,c_2],\quad[c_2,c_0],\quad[c_0,c_1]. \tag*{(198)} [ c 1 , c 2 ] , [ c 2 , c 0 ] , [ c 0 , c 1 ] . (198)
in the variable z = E 1 − m 2 z=E_1-m_2 z = E 1 − m 2 . As explained around (17) , the integral then vanishes as a consequence of the fact that the intervals in (S139) double back on themselves. As a sanity check, we first rederive this result using (S136), specialized to d = 4 d=4 d = 4 (and the ‘increasing’ definition of D a \mathcal{D}_a D a ). In this case κ = 2 \kappa=2 κ = 2 , so the κ − 1 \kappa-1 κ − 1 component vectors V a ( b ) V_a^{(b)} V a ( b ) are simply numbers denoting the value m 2 m_2 m 2 , and equal
V a ( b ) = c a + c b (199) V_a^{(b)}=c_a+c_b \tag*{(199)} V a ( b ) = c a + c b (199)
(S136) thus instructs us to integrate m 2 m_2 m 2 over the intervals
[ c 1 + c 0 , c 2 + c 0 ] , [ c 1 + c 0 , c 1 + c 2 ] , [ c 2 + c 0 , c 2 + c 1 ] , (200) [c_1+c_0,c_2+c_0],\quad[c_1+c_0,c_1+c_2],\quad[c_2+c_0,c_2+c_1], \tag*{(200)} [ c 1 + c 0 , c 2 + c 0 ] , [ c 1 + c 0 , c 1 + c 2 ] , [ c 2 + c 0 , c 2 + c 1 ] , (200)
but to weight three integrals above with the relative signs + + + , − - − and + + + respectively. Using E 1 = c 0 + c 1 + c 2 E_1=c_0+c_1+c_2 E 1 = c 0 + c 1 + c 2 , and absorbing the middle minus sign into a reversal of the contour, we see this exactly agrees with the integral of z z z over the contour (S139), as anticipated.
d=6
Let us now study the case d = 6 d=6 d = 6 . For the purposes of visualization, we assume in this subsubsection that c a c_a c a take real and distinct values; however the fact that I \mathcal{I} I is a polynomial in c a c_a c a allows for a straightforward analytic continuation, so all our final results also apply at complex values of c a c_a c a .
In this case the vectors V a ( b ) = V b ( a ) = p a b V_a^{(b)}=V_b^{(a)}=p_{ab} V a ( b ) = V b ( a ) = p ab are two component vectors ( m 2 , m 3 ) (m_2,m_3) ( m 2 , m 3 ) . The four regions D 0 \mathcal{D}_0 D 0 , D 1 \mathcal{D}_1 D 1 , D 2 \mathcal{D}_2 D 2 and D 3 \mathcal{D}_3 D 3 are each triangles on the m 2 , m 3 m_2,m_3 m 2 , m 3 plane. The vertices of the triangle corresponding to D a \mathcal{D}_a D a are the three points p a b p_{ab} p ab , b = 0 , … , 3 b=0,\ldots,3 b = 0 , … , 3 , b ≠ a b\ne a b = a , where
p a b = ( c a + c b , c a 2 + c a c b + c b 2 ) . (201) p_{ab}=\left(c_a+c_b,c_a^2+c_ac_b+c_b^2\right). \tag*{(201)} p ab = ( c a + c b , c a 2 + c a c b + c b 2 ) . (201)
Each of these four triangles shares exactly one vertex with every other triangle (the common vertex between D a \mathcal{D}_a D a and D b \mathcal{D}_b D b is p a b p_{ab} p ab ). According to (S136), the S ∘ ln Z β \mathcal{S}\circ\frac{\ln Z}{\beta} S ∘ β l n Z is obtained by computing the integral of the given two form over the surface
D 0 − D 1 + D 2 − D 3 . (202) \mathcal{D}_0-\mathcal{D}_1+\mathcal{D}_2-\mathcal{D}_3. \tag*{(202)} D 0 − D 1 + D 2 − D 3 . (202)
As the 12 components of the 6 vectors p a b p_{ab} p ab are all determined by four numbers c a c_a c a ; as a consequence the six vectors p a b p_{ab} p ab are far from generic. It will nonetheless prove illuminating to first study the integration domain (S143) for six generic vectors p a b p_{ab} p ab , and only subsequently specialize to p a b p_{ab} p ab given by (S142).
When p a b p_{ab} p ab are generic, the integration domain (S143) can be visualized as in Figure 1 below. D 0 \mathcal{D}_0 D 0 , D 1 \mathcal{D}_1 D 1 , D 2 \mathcal{D}_2 D 2 , and D 3 \mathcal{D}_3 D 3 are the four shaded triangles in Figure 1 ; note that every triangle shares exactly one common vertex with every other triangle. While Figure 1 has been drawn in a 3 dimensional manner, to aid visualization, the reader should mentally visualize the points p 02 p_{02} p 02 and p 13 p_{13} p 13 as being squashed inwards (towards the center of the figure) so that the entire octahedron of Figure 1 is flattened onto the single plane (the plane of p 12 , p 23 , p 03 , p 01 p_{12},p_{23},p_{03},p_{01} p 12 , p 23 , p 03 , p 01 ). If we visualize shaded triangles as triangular sheets of paper, the dark blue triangles carry one orientation (upper flap of the flat paper origami) and the two light blue triangles represent the opposite orientation (lower flap of the flat paper origami). The resultant flat origami (integration domain) lies on the ( m 2 , m 3 ) (m_2,m_3) ( m 2 , m 3 ) plane, and covers parts of this plane. While some portions of this plane are covered by only the upper flap (positive orientation), other portions are covered by only the lower flap (negative orientation) and still other portions are covered by both flaps. While the integral receives no contributions from the last region (as the integrals over oppositely oriented surfaces cancel), it receives contributions from the first and second regions, and so does, in general, evaluate to a nonzero result.
Continuing to work with generic p a b p_{ab} p ab , let us now study an augmented integration domain. Our augmented domain is defined to include also the four triangular holes (which can be visualized as white paper triangles) in Figure 1 (in addition to the four blue shaded triangles already studied above). Orientations are chosen so that the normal to every triangle is outward pointing. This augmented integration domain is a flat origami whose upper and lower flaps each consist of two blue and two white triangles, and can be thought of as a ‘closed kite shaped envelope’. When we paste this new flat origami onto the ( m 2 , m 3 ) (m_2,m_3) ( m 2 , m 3 ) plane, every covered point is covered by both an upper and a lower flap. As a consequence, the integral over the augmented integration domain simply vanishes for arbitrary choices of the six vectors p a b p_{ab} p ab .
Now the augmented integration domain effectively coincides with the actual domain (S143) when each of the four holes (white triangles) in Figure 1 has zero area, i.e. when the three vectors ( p a b , p a c , p b c ) (p_{ab},p_{ac},p_{bc}) ( p ab , p a c , p b c ) are collinear, for each of the four possible choices of the triplet ( a , b , c ) (a,b,c) ( a , b , c ) . This collinearity condition is met only at finely tuned choices for p a b p_{ab} p ab . As emphasized above, however, p a b p_{ab} p ab given by (S142) are very far from generic; and the collinearity conditions above are, in fact, always obeyed. One way of seeing this is to note (from (S142)) that the components ( m 2 , m 3 ) (m_2,m_3) ( m 2 , m 3 ) of each of the three vectors p a b p_{ab} p ab , p b c p_{bc} p b c , and p a c p_{ac} p a c obey the equation
m 3 = ( c a + c b + c c ) m 2 − ( c a c b + c a c c + c b c c ) . (203) m_3=(c_a+c_b+c_c)m_2-(c_ac_b+c_ac_c+c_bc_c). \tag*{(203)} m 3 = ( c a + c b + c c ) m 2 − ( c a c b + c a c c + c b c c ) . (203)
for each of the four choices of the triplet ( a , b , c ) (a,b,c) ( a , b , c ) . It follows that in the case under study, the original integration domain (S143) effectively coincides with the augmented integration domain, and the integration over (S143) actually vanishes, so that
S ∘ ( ln Z r o t β ) = 0 (204) \mathcal{S}\circ\left(\frac{\ln Z^{\mathrm{rot}}}{\beta}\right)=0 \tag*{(204)} S ∘ ( β ln Z rot ) = 0 (204)
as claimed.
Before generalizing to higher dimensions, it is interesting to pause to visualize the integration region (S143) in the physically relevant collinear case. Upon mentally squashing the octahedron of Figure 1 down to plane, in this case, we obtain a flattened origami of the form depicted in Figure 2 . Figure 2 has been plotted for the illustrative choice ( c 0 , c 1 , c 2 , c 3 ) = ( 0 , 1 , 2 , 3 ) (c_0,c_1,c_2,c_3)=(0,1,2,3) ( c 0 , c 1 , c 2 , c 3 ) = ( 0 , 1 , 2 , 3 ) . In order to conveniently display the triangles (without changing their incidence relations), the figure uses the equivalent coordinates ζ = m 2 \zeta=m_2 ζ = m 2 and η = m 3 − 4 m 2 + 4 \eta=m_3-4m_2+4 η = m 3 − 4 m 2 + 4 .
Figure 2. The four integration regions in d = 6 d=6 d = 6 for real ( c 0 , c 1 , c 2 , c 3 ) = ( 0 , 1 , 2 , 3 ) (c_0,c_1,c_2,c_3)=(0,1,2,3) ( c 0 , c 1 , c 2 , c 3 ) = ( 0 , 1 , 2 , 3 ) , shown in the coordinates ξ = m 2 \xi=m_2 ξ = m 2 , η = m 3 − 4 m 2 + 4 \eta=m_3-4m_2+4 η = m 3 − 4 m 2 + 4 . The three corners p 01 , p 02 , p 12 p_{01},p_{02},p_{12} p 01 , p 02 , p 12 lie on one straight line. The same statement holds for every choice of three labels, and the corresponding oriented boundary segments cancel.
We have explained above that the collinearity condition on p a b p_{ab} p ab ensures that the (originally open) integration domain (S143) actually effectively coincides with the closed augmented integration domain. This point can directly be understood from Figure 2 as follows. The integration region (S143) has four boundaries that lie along the four straight lines in Figure 2 . However these boundaries actually double back on each other, and so can (for the purposes of computing an integral) equally well be sewn together to form a closed surface (this closed surface is the augmented domain). For example, the part of the oriented boundary involving the labels 0 , 1 , 2 0,1,2 0 , 1 , 2 lies on the leftmost slanting line in Figure 2 , and equals
[ p 01 , p 02 ] − [ p 01 , p 12 ] + [ p 02 , p 12 ] . (205) [p_{01},p_{02}]-[p_{01},p_{12}]+[p_{02},p_{12}]. \tag*{(205)} [ p 01 , p 02 ] − [ p 01 , p 12 ] + [ p 02 , p 12 ] . (205)
A glance at Figure 2 will convince the reader that the three segments in (S146) lie on the same line, and the line segment (second term in (S146)) is the sum of the two shorter ones but with opposite orientation. Hence the integration domain does not really have a boundary. The same argument applies to each choice of three labels (each of the four straight lines in Figure 2 so the oriented boundary of
D 0 − D 1 + D 2 − D 3 (206) D_0-D_1+D_2-D_3 \tag*{(206)} D 0 − D 1 + D 2 − D 3 (206)
effectively vanishes, and the integration domain is effectively closed.
The vanishing of the integral over the domain depicted in Figure 2 can also be verified very explicitly as follows. In Figure 2 , the triangles ( p 01 , p 02 , p 03 ) (p_{01},p_{02},p_{03}) ( p 01 , p 02 , p 03 ) and ( p 20 , p 21 , p 23 ) (p_{20},p_{21},p_{23}) ( p 20 , p 21 , p 23 ) are positively oriented (their normal points out of the paper) and constitute the upper flap of the flattened origami. Together, these two triangles cover the shaded region once. On the other hand, the triangles ( p 10 , p 12 , p 13 ) (p_{10},p_{12},p_{13}) ( p 10 , p 12 , p 13 ) and ( p 30 , p 31 , p 32 ) (p_{30},p_{31},p_{32}) ( p 30 , p 31 , p 32 ) are effectively negatively oriented (because of the minus signs in (S143)); together they also cover the shaded region in Figure 2 . We thus see that every point on the integration domain in Figure 2 occurs twice; once with positive and once with negative orientation. Consequently the integral vanishes.
Finally, the vanishing of the integral over the surface of Figure 2 can also be argued in the following equivalent fashion. As the real ( m 2 , m 3 ) (m_2,m_3) ( m 2 , m 3 ) plane is contractible, the integrand two-form Υ \Upsilon Υ (that appears in (S136)) can be written as Υ = d α \Upsilon=d\alpha Υ = d α (recall that every top form is always closed, and the contractibility of the integration region guarantees that this closed form is also exact). Stokes’ theorem then gives
∫ D 0 Υ − ∫ D 1 Υ + ∫ D 2 Υ − ∫ D 3 Υ = 0 (207) \int_{\mathcal{D}_0}\Upsilon-\int_{\mathcal{D}_1}\Upsilon+\int_{\mathcal{D}_2}\Upsilon-\int_{\mathcal{D}_3}\Upsilon=0 \tag*{(207)} ∫ D 0 Υ − ∫ D 1 Υ + ∫ D 2 Υ − ∫ D 3 Υ = 0 (207)
where we have used that the boundary of the integration region is effectively trivial.
General even dimensions
We now turn to the generalization of the discussion above to every even dimension. In each such dimension, we have
G ∘ ( ln Z r o t β ) = 2 π κ ( κ + 1 ) V ( − 1 ) κ ∫ D Υ (208) \mathcal{G}\circ\left(\frac{\ln Z^{\mathrm{rot}}}{\beta}\right)=\frac{2\pi^\kappa}{(\kappa+1)\mathcal{V}}(-1)^\kappa\int_{\mathcal{D}}\Upsilon \tag*{(208)} G ∘ ( β ln Z rot ) = ( κ + 1 ) V 2 π κ ( − 1 ) κ ∫ D Υ (208)
where the integration domain D \mathcal{D} D is given by
D = D 0 − D 1 + D 2 − … + ( − 1 ) κ D κ . (209) \mathcal{D}=\mathcal{D}_0-\mathcal{D}_1+\mathcal{D}_2-\ldots+(-1)^\kappa\mathcal{D}_\kappa. \tag*{(209)} D = D 0 − D 1 + D 2 − … + ( − 1 ) κ D κ . (209)
Here D a \mathcal{D}_a D a is the κ − 1 \kappa-1 κ − 1 dimensional simplex constructed by the κ \kappa κ vectors p a b p_{ab} p ab , ( b = 0 … κ , b ≠ a ) (b=0\ldots\kappa,\ b\ne a) ( b = 0 … κ , b = a ) , with the ‘increasing’ orientation. Note that this simplex has κ \kappa κ distinct corners (these are the vectors p a b p_{ab} p ab , with b ≠ a b\ne a b = a ). These simplices are line intervals when κ = 2 \kappa=2 κ = 2 (see (S146)), triangles when κ = 3 \kappa=3 κ = 3 (see Figure 1 ) and tetrahedra when κ = 4 \kappa=4 κ = 4 . They are simply called ( κ − 1 ) (\kappa-1) ( κ − 1 ) simplices) for κ ≥ 5 \kappa\ge5 κ ≥ 5 .
(S150) tells us that the integration domain is the union of κ + 1 \kappa+1 κ + 1 distinct simplices. Each simplex shares exactly one common corner (or vertex) with every other simplex. As in our d = 6 d=6 d = 6 discussion above, we first study the integration domain for arbitrary values of the κ − 1 \kappa-1 κ − 1 component vectors p a b p_{ab} p ab (the components being ( m 2 , … , m κ ) (m_2,\ldots,m_\kappa) ( m 2 , … , m κ ) ), and only later examine the implications of the fact that these ( κ + 1 ) κ 2 \frac{(\kappa+1)\kappa}{2} 2 ( κ + 1 ) κ ( κ − 1 ) (\kappa-1) ( κ − 1 ) component vectors are actually determined by the κ + 1 \kappa+1 κ + 1 numbers c a c_a c a via Eq. (192) .
In our d = 6 d=6 d = 6 discussion above, we have explained above (see around Figure 1 ) that the integration domain for generic p a b p_{ab} p ab can be visualized as consisting of four of the eight flat surfaces of a 3d solid octahedron. The generalization of this statement is the following. Topologically speaking, the integration domain in d = 2 κ d=2\kappa d = 2 κ , κ ≥ 3 \kappa\ge3 κ ≥ 3 , consists of κ + 1 \kappa+1 κ + 1 of the 2 ( κ + 1 ) 2(\kappa+1) 2 ( κ + 1 ) flat boundaries of κ \kappa κ dimensional solid surface called a Δ ( 2 , κ + 1 ) \Delta(2,\kappa+1) Δ ( 2 , κ + 1 ) , which we now describe in detail.
Consider a Cartesian R κ + 1 \mathbb{R}^{\kappa+1} R κ + 1 space. Δ ( 2 , κ + 1 ) \Delta(2,\kappa+1) Δ ( 2 , κ + 1 ) is the intersection of the plane ∑ a t a = 2 \sum_a t_a=2 ∑ a t a = 2 with the unit cube of this Cartesian space. In equations
Δ ( 2 , κ + 1 ) : = { ( t 0 , … , t κ ) | 0 ≤ t a ≤ 1 , ∑ a = 0 κ t a = 2 } . (210) \Delta(2,\kappa+1):=\left\{(t_0,\ldots,t_\kappa)\,\middle|\,0\le t_a\le1,\ \sum_{a=0}^{\kappa}t_a=2\right\}. \tag*{(210)} Δ ( 2 , κ + 1 ) := { ( t 0 , … , t κ ) 0 ≤ t a ≤ 1 , a = 0 ∑ κ t a = 2 } . (210)
This shape is easily visualized in the case κ = 2 \kappa=2 κ = 2 ; see Figure 3 where it consists of the interior of a triangle. The boundaries of this triangle are the three integration domains D 0 \mathcal{D}_0 D 0 , D 1 \mathcal{D}_1 D 1 and D 2 \mathcal{D}_2 D 2 , together with the three red points in this figure. The fact that the red dots are of one lower dimension than the integration domains is a non generic feature that does not persist to κ ≥ 3 \kappa\ge3 κ ≥ 3 . At these values of κ \kappa κ , this κ \kappa κ dimensional ‘polytope’ (see Eq. (210) ) has two different kinds of flat κ − 1 \kappa-1 κ − 1 dimensional boundaries; first the κ + 1 \kappa+1 κ + 1 ‘shaded’ surfaces t a = 1 t_a=1 t a = 1 , ( a = 0 … κ ) (a=0\ldots\kappa) ( a = 0 … κ ) , and second the κ + 1 \kappa+1 κ + 1 ‘white’ surfaces t a = 0 t_a=0 t a = 0 , ( a = 0 … κ ) (a=0\ldots\kappa) ( a = 0 … κ ) . Topologically speaking, we identify the a t h a^{\mathrm{th}} a th shaded surface t a = 1 t^a=1 t a = 1 with our integration surfaces D a \mathcal{D}_a D a , and the a t h a^{\mathrm{th}} a th ‘white’ surface t a = 0 t_a=0 t a = 0 with ‘holes’ between these integration surfaces.
The identification spelled out above can be justified as follows. Notice that the surface element t a = 1 t^a=1 t a = 1 is given by the equation ∑ b ≠ a t b = 1 \sum_{b\ne a}t^b=1 ∑ b = a t b = 1 , b ≠ a b\ne a b = a , t b > 0 t^b>0 t b > 0 , and so defines a ( κ − 1 ) (\kappa-1) ( κ − 1 ) simplex. Moreover, the a t h a^{\mathrm{th}} a th simplex touches the b t h b^{\mathrm{th}} b th simplex at exactly one point t a = t b = 1 t_a=t_b=1 t a = t b = 1 . This is exactly the connectivity of the D a \mathcal{D}_a D a above, justifying our identification. Note that it follows from this discussion that the corners t a = t b = 1 t_a=t_b=1 t a = t b = 1 , b = 0 … κ b=0\ldots\kappa b = 0 … κ , b ≠ a b\ne a b = a should be topologically identified with p a b p_{ab} p ab ).
The full boundary of Δ ( 2 , κ + 1 ) \Delta(2,\kappa+1) Δ ( 2 , κ + 1 ) is a closed oriented surface; topologically speaking, our integration domain consists of a part of this surface. We refer to the remainder of this surface as holes. The holes on this surface are made up of the ( κ + 1 ) (\kappa+1) ( κ + 1 ) patches t a = 0 t^a=0 t a = 0 . 31 It follows immediately from the definition (S151), that each of these ‘holes’ is, itself, a
Δ ( 2 , κ ) \Delta(2,\kappa) Δ ( 2 , κ ) . 32 Notice that the hole t a = 0 t^a=0 t a = 0 shares a boundary with each of the shaded surfaces t b = 1 t^b=1 t b = 1 with b ≠ a b\ne a b = a . Clearly, the common boundary between these surfaces is itself a κ − 2 \kappa-2 κ − 2 dimensional simplex constructed out of the κ − 1 \kappa-1 κ − 1 vectors
p c b , c = 0 … κ , c ≠ b , c ≠ a . (211) p_{cb},\quad c=0\ldots\kappa,\ c\ne b,\ c\ne a. \tag*{(211)} p c b , c = 0 … κ , c = b , c = a . (211)
In addition, the hole t a = 0 t^a=0 t a = 0 also shares a boundary with the hole t b = 0 t^b=0 t b = 0 , for all b ≠ a b\ne a b = a . It follows from definitions that this common boundary is, in turn, a Δ ( 2 , κ − 1 ) \Delta(2,\kappa-1) Δ ( 2 , κ − 1 ) .
We reemphasize that the discussion of the previous paragraphs describes our integration domain only in a topological sense. The R κ + 1 \mathbb{R}^{\kappa+1} R κ + 1 space in which (S151) is embedded is purely fictional (it has nothing to do with the physical space parameterized by m i m_i m i ). The precise statement is that there exists a continuous map from the surface of the polytope (S151) into the R κ − 1 \mathbb{R}^{\kappa-1} R κ − 1 parameterized by m 2 … m κ m_2\ldots m_\kappa m 2 … m κ , such that the shaded surfaces t a = 1 t_a=1 t a = 1 map to D a \mathcal{D}_a D a , the a a a th component of the integration domain D a \mathcal{D}_a D a . Under the same map, the ‘white’ surfaces t a = 0 t_a=0 t a = 0 map to holes in the integration domain.
In the physical problem of interest, our integration surfaces D a \mathcal{D}_a D a are given and fixed. On the other hand the holes H a \mathcal{H}_a H a are, of course, not specified; we may take them to be any surfaces that complete the integration contour D \mathcal{D} D into a closed oriented contour. The only thing that is fixed about these surfaces is their κ − 2 \kappa-2 κ − 2 dimensional boundaries with the κ \kappa κ integration regions D b \mathcal{D}_b D b , b ≠ a b\ne a b = a . This κ − 2 \kappa-2 κ − 2 dimensional boundary is itself a simplex generated by the κ − 1 \kappa-1 κ − 1 vectors p b c p_{bc} p b c , c ≠ a c\ne a c = a , c ≠ b c\ne b c = b (as mentioned, we have one such boundary for each D b \mathcal{D}_b D b , b ≠ a b\ne a b = a ).
We denote this κ − 1 \kappa-1 κ − 1 dimensional oriented region of R κ − 1 \mathbb{R}^{\kappa-1} R κ − 1 (parameterized by m i m_i m i ) as H a \mathcal{H}_a H a . 33
In the discussion above we have characterized the ‘shaded integration surfaces’ and the ‘white holes’ in every κ \kappa κ ; however our characterization was somewhat abstract. As a brief aside, in the table below we provide an explicit listing of the shape of the solid surfaces (κ − 1 \kappa-1 κ − 1 simplices) and holes (Δ ( 2 , κ ) \Delta(2,\kappa) Δ ( 2 , κ ) ) in low dimensions:
Table 1.
As an aside for the interested reader, we pause to describe the case d = 8 d = 8 d = 8 in a little more detail (the reader who finds herself uninterested in this exercise in visualization can safely skip to the next paragraph). In this case the
polytope is Δ ( 2 , 5 ) \Delta(2,5) Δ ( 2 , 5 ) , a four-dimensional solid, usually called the rectified 5-cell (see the table above). As Δ ( 2 , 5 ) \Delta(2,5) Δ ( 2 , 5 ) is four dimensional it is hard to visualize. However its boundary components are three dimensional, and so can be visualized. The boundary consists of five tetrahedra t a = 1 t_a = 1 t a = 1 (these constitute our integration domain) and five octahedra t a = 0 t_a = 0 t a = 0 (these constitute our holes). Thus the five terms in the cyclic sum are represented by tetrahedral integration regions, while the five additional faces are octahedra. Figure 4 displays the two kinds of three-dimensional boundary cells.
Figure 4. The boundary cells of Δ ( 2 , 5 ) \Delta(2,5) Δ ( 2 , 5 ) in d = 8 d = 8 d = 8 . There are five tetrahedral faces t a = 1 t_a = 1 t a = 1 , one for each term in the cyclic sum, and five octahedral faces t a = 0 t_a = 0 t a = 0 .
The remaining discussion proceeds as in d = 6 d = 6 d = 6 . As the integrand on the RHS (S149) is (order by order) a polynomial (hence analytic) in the κ − 1 \kappa- 1 κ − 1 m i m_i m i , its integral over any closed κ − 1 \kappa- 1 κ − 1 dimensional surface vanishes as a consequence of Stokes’s theorem. Applying this to the map of the boundary of the polytope Δ ( 2 , κ + 1 ) \Delta(2,\kappa+ 1) Δ ( 2 , κ + 1 ) , we conclude that the RHS of (S149) vanishes when the integration domain D \mathcal{D} D is generalized to D + H \mathcal{D} + \mathcal{H} D + H where
H = ∑ a = 0 κ H a . (212) \mathcal{H} = \sum_{a=0}^{\kappa} \mathcal{H}_a . \tag*{(212)} H = a = 0 ∑ κ H a . (212)
In equations
∫ D + H Υ = 0. (213) \int_{\mathcal{D}+\mathcal{H}} \Upsilon= 0 . \tag*{(213)} ∫ D + H Υ = 0. (213)
As in d = 6 d = 6 d = 6 , this is the most we can say when p a b p_{ab} p ab are arbitrary vectors. As in d = 6 d = 6 d = 6 , however, it is very important that p a b p_{ab} p ab are not actually arbitrary, but are instead given by Eq. (192) . This has the following crucial consequence. Recall that we are free to choose the shapes of the holes H a \mathcal{H}_a H a subject only to the following constraints; each of κ \kappa κ boundaries of the region H a \mathcal{H}_a H a with the integration domain D b \mathcal{D}_b D b is given by Eq. (211) , (for the κ \kappa κ values of b = 0 , … κ b = 0, \ldots\kappa b = 0 , … κ , b ≠ a b \ne a b = a ). In addition, the boundary of the hole H a \mathcal{H}_a H a with the hole H b \mathcal{H}_b H b (for each of the κ \kappa κ possible value of b b b with b ≠ a b \ne a b = a ) must, of course, match with the boundary of H b \mathcal{H}_b H b with H a \mathcal{H}_a H a .
In the subsequent paragraph, we will demonstrate that each of the vectors in Eq. (211) actually lie in a particular κ − 2 \kappa- 2 κ − 2 dimensional hyperplane of R κ − 1 \mathbb{R}^{\kappa-1} R κ − 1 ; the same hyperplane for each of the values of b b b listed above (i.e. for each b ≠ a b \ne a b = a 34 35 Since all boundaries of the hole H a \mathcal{H}_a H a with the fixed integration regions D b \mathcal{D}_b D b lie in the same κ − 2 \kappa-2 κ − 2 dimensional hyperplane, it follows that region H a \mathcal{H}_a H a can be chosen to lie entirely in the same κ − 2 \kappa-2 κ − 2 hyperplane.36 With this choice, the integral over this surface vanishes. Since this is true for every value of a a a , the integral over H \mathcal{H} H vanishes. Consequently (S154) becomes
∫ D R = 0 (214) \int_{\mathcal{D}}\mathfrak{R}=0 \tag*{(214)} ∫ D R = 0 (214)
and it follows from (S149) that
G ∘ ( ln Z r o t β ) = 0 \mathcal{G}\circ\left(\frac{\ln Z^{\mathrm{rot}}}{\beta}\right)=0 G ∘ ( β ln Z rot ) = 0
as we set out to prove.
As promised above, we now demonstrate that the vectors p b d p_{bd} p b d with b ≠ a b\ne a b = a and d ≠ a d\ne a d = a all lie in a given κ − 2 \kappa-2 κ − 2 plane. Define
q a ( t ) : = ∏ m ≠ a ( t − c m ) = t κ − e 1 ( a ) t κ − 1 + e 2 ( a ) t κ − 2 − ⋯ + ( − 1 ) κ e κ ( a ) , (215) q_a(t):=\prod_{m\ne a}(t-c_m)=t^\kappa-e_1^{(a)}t^{\kappa-1}+e_2^{(a)}t^{\kappa-2}-\cdots+(-1)^\kappa e_\kappa^{(a)}, \tag*{(215)} q a ( t ) := m = a ∏ ( t − c m ) = t κ − e 1 ( a ) t κ − 1 + e 2 ( a ) t κ − 2 − ⋯ + ( − 1 ) κ e κ ( a ) , (215)
(notice the product above runs over all m ≠ a m\ne a m = a ). Now consider some d ≠ a d\ne a d = a and another b ≠ a b\ne a b = a . It follows immediately from the definition (S156) that q a ( c d ) = q a ( c b ) = 0 q_a(c_d)=q_a(c_b)=0 q a ( c d ) = q a ( c b ) = 0 . Consequently q a ( c d ) − q a ( c b ) = 0 q_a(c_d)-q_a(c_b)=0 q a ( c d ) − q a ( c b ) = 0 . Dividing this by c d − c b c_d-c_b c d − c b , using (S156) and the definition (S127), we conclude that
m κ − e 1 ( a ) m κ − 1 + e 2 ( a ) m κ − 2 − ⋯ + ( − 1 ) κ − 1 e κ − 1 ( a ) = 0 , (216) m_\kappa-e_1^{(a)}m_{\kappa-1}+e_2^{(a)}m_{\kappa-2}-\cdots+(-1)^{\kappa-1}e_{\kappa-1}^{(a)}=0, \tag*{(216)} m κ − e 1 ( a ) m κ − 1 + e 2 ( a ) m κ − 2 − ⋯ + ( − 1 ) κ − 1 e κ − 1 ( a ) = 0 , (216)
where m j m_j m j are the components of the vector p d b p_{db} p d b . Recall that (S157) holds for the components of any p d b p_{db} p d b , for any choice of d , b ≠ a d,b\ne a d , b = a . Since (S157) defines a codimension one hyperplane in the R κ − 1 \mathbb{R}^{\kappa-1} R κ − 1 parameterized by the m j m_j m j , it follows that the simplices that make up all the boundaries of the a t h a^{\mathrm{th}} a th hole lie in this hyperplane, as we needed to prove.
Evaluation of cyclic sum of the Kerr-AdS2 κ + 1 _{2\kappa+1} 2 κ + 1 black hole partition function
In this small section, we will derive the cyclic identity for the Kerr-AdS2 κ + 1 _{2\kappa+1} 2 κ + 1 black hole partition function. We start with the expression ln Z B H β \frac{\ln Z_{\mathrm{BH}}}{\beta} β l n Z BH as written in (36). We apply Ω a \Omega^a Ω a (Ω \Omega Ω or Ω b h \Omega_{\mathrm{bh}} Ω bh as defined in (37)) on it and it gives us the following
Ω a ∘ [ ln Z B H β ] = π κ − 1 8 ( κ − 1 ) ! G 2 κ + 1 ( 1 − q a 2 ) ∏ i = 0 i ≠ a κ 1 + q i 2 q a 2 − q i 2 \Omega^a\circ\left[\frac{\ln Z_{\mathrm{BH}}}{\beta}\right]
=\frac{\pi^{\kappa-1}}{8(\kappa-1)!G_{2\kappa+1}}(1-q_a^2)\prod_{\substack{i=0\\i\ne a}}^\kappa\frac{1+q_i^2}{q_a^2-q_i^2} Ω a ∘ [ β ln Z BH ] = 8 ( κ − 1 )! G 2 κ + 1 π κ − 1 ( 1 − q a 2 ) i = 0 i = a ∏ κ q a 2 − q i 2 1 + q i 2
= π κ − 1 8 ( κ − 1 ) ! G 2 κ + 1 [ ∏ j = 0 κ ( 1 + q j 2 ) ] 1 − q a 2 1 + q a 2 ∏ i = 0 i ≠ a κ 1 q a 2 − q i 2 , for a = 0 , 1 , ⋯ , κ . (217) \qquad=\frac{\pi^{\kappa-1}}{8(\kappa-1)!G_{2\kappa+1}}
\left[\prod_{j=0}^\kappa(1+q_j^2)\right]\frac{1-q_a^2}{1+q_a^2}\prod_{\substack{i=0\\i\ne a}}^\kappa\frac{1}{q_a^2-q_i^2},
\qquad\text{for }a=0,1,\cdots,\kappa. \tag*{(217)} = 8 ( κ − 1 )! G 2 κ + 1 π κ − 1 [ j = 0 ∏ κ ( 1 + q j 2 ) ] 1 + q a 2 1 − q a 2 i = 0 i = a ∏ κ q a 2 − q i 2 1 , for a = 0 , 1 , ⋯ , κ . (217)
Summing over a a a from 0 to κ \kappa κ , we obtain
( 1 + Ω + ⋯ + Ω κ ) ∘ [ ln Z B H β ] = π κ − 1 8 ( κ − 1 ) ! G 2 κ + 1 [ ∏ j = 0 κ ( 1 + q j 2 ) ] ∑ a = 0 κ 1 − q a 2 1 + q a 2 ∏ i = 0 i ≠ a κ 1 q a 2 − q i 2 . (218) (1+\Omega+\cdots+\Omega^\kappa)\circ\left[\frac{\ln Z_{\mathrm{BH}}}{\beta}\right]
=\frac{\pi^{\kappa-1}}{8(\kappa-1)!G_{2\kappa+1}}
\left[\prod_{j=0}^\kappa(1+q_j^2)\right]\sum_{a=0}^\kappa\frac{1-q_a^2}{1+q_a^2}\prod_{\substack{i=0\\i\ne a}}^\kappa\frac{1}{q_a^2-q_i^2}. \tag*{(218)} ( 1 + Ω + ⋯ + Ω κ ) ∘ [ β ln Z BH ] = 8 ( κ − 1 )! G 2 κ + 1 π κ − 1 [ j = 0 ∏ κ ( 1 + q j 2 ) ] a = 0 ∑ κ 1 + q a 2 1 − q a 2 i = 0 i = a ∏ κ q a 2 − q i 2 1 . (218)
We will evaluate the a a a sum by using contour integration method. To do that, we will define the following function f ( z ) f(z) f ( z ) such that
f ( z ) : = 1 − z 1 + z ∏ i = 0 κ 1 z − q i 2 . (219) f(z):=\frac{1-z}{1+z}\prod_{i=0}^\kappa\frac{1}{z-q_i^2}. \tag*{(219)} f ( z ) := 1 + z 1 − z i = 0 ∏ κ z − q i 2 1 . (219)
We can see that f ( z ) f(z) f ( z ) has simple poles at z = q a 2 z=q_a^2 z = q a 2 for a = 0 , 1 , ⋯ , κ a=0,1,\cdots,\kappa a = 0 , 1 , ⋯ , κ and also at z = − 1 z=-1 z = − 1 . For the large value of ∣ z ∣ |z| ∣ z ∣ , the behavior of f ( z ) ∼ − 1 z κ + 1 f(z)\sim-\frac{1}{z^{\kappa+1}} f ( z ) ∼ − z κ + 1 1 . So f ( z ) f(z) f ( z ) falls off at least as fast as 1 z 2 \frac{1}{z^2} z 2 1 for κ ≥ 1 \kappa\geq1 κ ≥ 1 . Hence, we conclude that the contour integration of f ( z ) f(z) f ( z ) on a circle (with center at the origin of the complex z z z plane) vanishes as its radius tends to infinity. Using the residue theorem, we can write
∑ a = 0 κ Res z = q a 2 f ( z ) + Res z = − 1 f ( z ) = 0. (220) \sum_{a=0}^{\kappa}\operatorname{Res}_{z=q_a^2}f(z)+\operatorname{Res}_{z=-1}f(z)=0. \tag*{(220)} a = 0 ∑ κ Res z = q a 2 f ( z ) + Res z = − 1 f ( z ) = 0. (220)
The residues of f ( z ) f(z) f ( z ) at z = q a 2 z=q_a^2 z = q a 2 are given by
Res z = q a 2 f ( z ) = 1 − q a 2 1 + q a 2 ∏ i = 0 i ≠ a κ 1 q a 2 − q i 2 , (221) \operatorname{Res}_{z=q_a^2}f(z)=\frac{1-q_a^2}{1+q_a^2}\prod_{\substack{i=0\\i\ne a}}^{\kappa}\frac{1}{q_a^2-q_i^2}, \tag*{(221)} Res z = q a 2 f ( z ) = 1 + q a 2 1 − q a 2 i = 0 i = a ∏ κ q a 2 − q i 2 1 , (221)
and the residue of f ( z ) f(z) f ( z ) at z = − 1 z=-1 z = − 1 is given by
Res z = − 1 f ( z ) = 2 ∏ j = 0 κ 1 ( − 1 − q j 2 ) = − 2 ( − 1 ) κ ∏ j = 0 κ 1 ( 1 + q j 2 ) . (222) \operatorname{Res}_{z=-1}f(z)=2\prod_{j=0}^{\kappa}\frac{1}{(-1-q_j^2)}=-2(-1)^\kappa\prod_{j=0}^{\kappa}\frac{1}{(1+q_j^2)}. \tag*{(222)} Res z = − 1 f ( z ) = 2 j = 0 ∏ κ ( − 1 − q j 2 ) 1 = − 2 ( − 1 ) κ j = 0 ∏ κ ( 1 + q j 2 ) 1 . (222)
Substituting the residues into (220) , we get
∑ a = 0 κ 1 − q a 2 1 + q a 2 ∏ i = 0 i ≠ a κ 1 q a 2 − q i 2 = 2 ( − 1 ) κ ∏ j = 0 κ 1 ( 1 + q j 2 ) . (223) \sum_{a=0}^{\kappa}\frac{1-q_a^2}{1+q_a^2}\prod_{\substack{i=0\\i\ne a}}^{\kappa}\frac{1}{q_a^2-q_i^2}=2(-1)^\kappa\prod_{j=0}^{\kappa}\frac{1}{(1+q_j^2)}. \tag*{(223)} a = 0 ∑ κ 1 + q a 2 1 − q a 2 i = 0 i = a ∏ κ q a 2 − q i 2 1 = 2 ( − 1 ) κ j = 0 ∏ κ ( 1 + q j 2 ) 1 . (223)
Substituting the above identity in (218) , we have obtained the (224)
( 1 + Ω + ⋯ + Ω κ ) ∘ [ ln Z B H β ] = ( − 1 ) κ π κ − 1 4 ( κ − 1 ) ! G 2 κ + 1 = ( − 1 ) κ κ ! a 2 κ (224) \left(1+\Omega+\cdots+\Omega^\kappa\right)\circ\left[\frac{\ln Z_{\mathrm{BH}}}{\beta}\right]=(-1)^\kappa\frac{\pi^{\kappa-1}}{4(\kappa-1)!G_{2\kappa+1}}=(-1)^\kappa\kappa!a_{2\kappa} \tag*{(224)} ( 1 + Ω + ⋯ + Ω κ ) ∘ [ β ln Z BH ] = ( − 1 ) κ 4 ( κ − 1 )! G 2 κ + 1 π κ − 1 = ( − 1 ) κ κ ! a 2 κ (224)
where the a a a anomaly a 2 κ a_{2\kappa} a 2 κ in d = 2 κ d=2\kappa d = 2 κ dimensional holographic CFT is a 2 κ = π κ − 1 4 κ κ ! ( κ − 1 ) ! G 2 κ + 1 a_{2\kappa}=\frac{\pi^{\kappa-1}}{4^\kappa\kappa!(\kappa-1)!G_{2\kappa+1}} a 2 κ = 4 κ κ ! ( κ − 1 )! G 2 κ + 1 π κ − 1 .
Spectral equivalence between S 3 × R S^3\times\mathbb{R} S 3 × R and A d S 3 × S 1 AdS_3\times S^1 A d S 3 × S 1
We consider a conformally coupled scalar on S 3 × R S^3\times\mathbb{R} S 3 × R which satisfies the following equation,
( □ − ξ R S 3 ) Φ ( x ) = 0 (225) (\Box-\xi R_{S^3})\Phi(x)=0 \tag*{(225)} ( □ − ξ R S 3 ) Φ ( x ) = 0 (225)
The metric of S 3 × R S^3\times\mathbb{R} S 3 × R in the Hopf coordinates is given by,
d s S 3 × R 2 = − d t 2 + d θ 2 + sin 2 θ d ϕ 1 2 + cos 2 θ d ϕ 2 2 , (226) ds^2_{S^3\times\mathbb{R}}=-dt^2+d\theta^2+\sin^2\theta\,d\phi_1^2+\cos^2\theta\,d\phi_2^2, \tag*{(226)} d s S 3 × R 2 = − d t 2 + d θ 2 + sin 2 θ d ϕ 1 2 + cos 2 θ d ϕ 2 2 , (226)
where the scalar modes can be written as
Φ = e − i E t Y n , m , p ( θ , ϕ 1 , ϕ 2 ) , n , m ∈ Z . (227) \Phi= e^{-iEt}Y_{n,m,p}(\theta,\phi_1,\phi_2), \quad n,m \in\mathbb{Z}. \tag*{(227)} Φ = e − i E t Y n , m , p ( θ , ϕ 1 , ϕ 2 ) , n , m ∈ Z . (227)
where the scalar harmonics Y n , m , p ( θ , ϕ 1 , ϕ 2 ) Y_{n,m,p}(\theta,\phi_1,\phi_2) Y n , m , p ( θ , ϕ 1 , ϕ 2 ) on S 3 S^3 S 3 can be written as
Y n , m , p ( θ , ϕ 1 , ϕ 2 ) ∝ e i n ϕ 1 + i m ϕ 2 ( sin θ ) ∣ n ∣ ( cos θ ) ∣ m ∣ P p ( ∣ n ∣ , ∣ m ∣ ) ( cos 2 θ ) , p = 0 , 1 , 2 , … , (228) Y_{n,m,p}(\theta,\phi_1,\phi_2) \propto e^{in\phi_1+im\phi_2}(\sin\theta)^{|n|}(\cos\theta)^{|m|}P_p^{(|n|,|m|)}(\cos2\theta), \quad p=0,1,2,\ldots, \tag*{(228)} Y n , m , p ( θ , ϕ 1 , ϕ 2 ) ∝ e in ϕ 1 + im ϕ 2 ( sin θ ) ∣ n ∣ ( cos θ ) ∣ m ∣ P p ( ∣ n ∣ , ∣ m ∣ ) ( cos 2 θ ) , p = 0 , 1 , 2 , … , (228)
where, P p ( ∣ n ∣ , ∣ m ∣ ) ( z ) P_p^{(|n|,|m|)}(z) P p ( ∣ n ∣ , ∣ m ∣ ) ( z ) is the Jacobi polynomial of degree p p p .
Scalar harmonics Y n , m , p Y_{n,m,p} Y n , m , p of S 3 S^3 S 3 satisfy
− ∇ S 3 2 Y l = l ( l + 2 ) Y l l = ∣ n ∣ + ∣ m ∣ + 2 p . (229) -\nabla^2_{S^3}Y_l=l(l+2)Y_l \qquad l=|n|+|m|+2p. \tag*{(229)} − ∇ S 3 2 Y l = l ( l + 2 ) Y l l = ∣ n ∣ + ∣ m ∣ + 2 p . (229)
Using Eq. (229) and including the contribution of the conformal coupling ξ R S 3 = 1 6 × 6 = 1 \xi R_{S^3}=\frac{1}{6}\times6=1 ξ R S 3 = 6 1 × 6 = 1 to Eq. (225) , we obtain
E 2 = l ( l + 2 ) + 1 = ( l + 1 ) 2 . (230) E^2=l(l+2)+1=(l+1)^2. \tag*{(230)} E 2 = l ( l + 2 ) + 1 = ( l + 1 ) 2 . (230)
Finally, we obtain the energy as
E S 3 × R = ∣ n ∣ + ∣ m ∣ + 2 p + 1. (231) E_{S^3\times\mathbb{R}}=|n|+|m|+2p+1. \tag*{(231)} E S 3 × R = ∣ n ∣ + ∣ m ∣ + 2 p + 1. (231)
Next, we perform the following coordinate change,
l = sin 2 θ = 1 cosh 2 ρ , (232) l=\sin^2\theta=\frac{1}{\cosh^2\rho}, \tag*{(232)} l = sin 2 θ = cosh 2 ρ 1 , (232)
and rewrite the metric of S 3 × R S^3\times\mathbb{R} S 3 × R as A d S 3 × S 1 AdS_3\times S^1 A d S 3 × S 1 up to some Weyl factor. The metric takes the form,
d s S 3 × R 2 = W 2 [ d ϕ 1 2 + d ρ 2 − cosh 2 ρ d t 2 + sinh 2 ρ d ϕ 2 2 ] = 1 cosh 2 ρ d s A d S 3 × S 1 2 ; W 2 = 1 cosh 2 ρ (233) ds^2_{S^3\times\mathbb{R}}=W^2\left[d\phi_1^2+d\rho^2-\cosh^2\rho\,dt^2+\sinh^2\rho\,d\phi_2^2\right]=\frac{1}{\cosh^2\rho}ds^2_{AdS_3\times S^1};\quad W^2=\frac{1}{\cosh^2\rho} \tag*{(233)} d s S 3 × R 2 = W 2 [ d ϕ 1 2 + d ρ 2 − cosh 2 ρ d t 2 + sinh 2 ρ d ϕ 2 2 ] = cosh 2 ρ 1 d s A d S 3 × S 1 2 ; W 2 = cosh 2 ρ 1 (233)
where, d s A d S 3 × S 1 2 ds^2_{AdS_3\times S^1} d s A d S 3 × S 1 2 is the metric of A d S 3 × S 1 AdS_3\times S^1 A d S 3 × S 1 , with S 1 S^1 S 1 parametrized by ϕ 1 \phi_1 ϕ 1 . Moreover, we impose smoothness of the scalar field where the ϕ 1 \phi_1 ϕ 1 circle shrinks, i.e.,
θ = 0 , l = sin 2 θ → 0 , (234) \theta=0,\quad l=\sin^2\theta\to0, \tag*{(234)} θ = 0 , l = sin 2 θ → 0 , (234)
and locally, the metric takes the form
d s 2 ≈ d r 2 + r 2 d ϕ 1 2 + ⋯ , r ≈ sin θ = l . (235) ds^2\approx dr^2+r^2d\phi_1^2+\cdots,\qquad r\approx\sin\theta=\sqrt{l}. \tag*{(235)} d s 2 ≈ d r 2 + r 2 d ϕ 1 2 + ⋯ , r ≈ sin θ = l . (235)
For a mode with angular momentum n n n
Φ ∼ e i n ϕ 1 \Phi\sim e^{in\phi_1} Φ ∼ e in ϕ 1
Hence, the smoothness at the origin implies
Φ S 3 ∼ r ∣ n ∣ ∼ l ∣ n ∣ / 2 . (236) \Phi_{S^3}\sim r^{|n|}\sim l^{|n|/2}. \tag*{(236)} Φ S 3 ∼ r ∣ n ∣ ∼ l ∣ n ∣/2 . (236)
Upon using Eq. (232) , this gives
Φ S 3 ∼ ( cosh ρ ) − ∣ n ∣ . (237) \Phi_{S^3}\sim(\cosh\rho)^{-|n|}. \tag*{(237)} Φ S 3 ∼ ( cosh ρ ) − ∣ n ∣ . (237)
Since the scalar has Weyl weight one, we obtain
Φ A d S 3 × S 1 = W Φ S 3 ∼ ( cosh ρ ) − ( ∣ n ∣ + 1 ) , ρ → ∞ . (238) \Phi_{AdS_3\times S^1}=W\Phi_{S^3}\sim(\cosh\rho)^{-(|n|+1)},\qquad\rho\to\infty. \tag*{(238)} Φ A d S 3 × S 1 = W Φ S 3 ∼ ( cosh ρ ) − ( ∣ n ∣ + 1 ) , ρ → ∞. (238)
Thus, the smoothness boundary condition at the shrinking ϕ i \phi_i ϕ i corresponds to the normalizable boundary condition on A d S 3 AdS_3 A d S 3 .
For a conformally coupled scalar on A d S 3 × S 1 AdS_3\times S^1 A d S 3 × S 1 , if we expand it along the non-contractible circle,
Φ A d S 3 × S 1 = e i n ϕ 1 φ n , (239) \Phi_{AdS_3\times S^1}=e^{in\phi_1}\varphi_n, \tag*{(239)} Φ A d S 3 × S 1 = e in ϕ 1 φ n , (239)
the Kaluza–Klein momentum contributes n 2 n^2 n 2 , and conformal coupling contributes − 1 -1 − 1 . Therefore the effective A d S 3 AdS_3 A d S 3 mass is
m n 2 = n 2 − 1. (240) m_n^2 = n^2 - 1. \tag*{(240)} m n 2 = n 2 − 1. (240)
Using the AdS-CFT map, we obtain
m n 2 = Δ n ( Δ n − 2 ) . ⟹ Δ n = 1 ± ∣ n ∣ (241) m_n^2 = \Delta_n(\Delta_n - 2). \quad\Longrightarrow\quad\Delta_n = 1 \pm|n| \tag*{(241)} m n 2 = Δ n ( Δ n − 2 ) . ⟹ Δ n = 1 ± ∣ n ∣ (241)
Next, using the falloff condition in Eq. (238) we obtain,
Δ n = ∣ n ∣ + 1. (242) \Delta_n = |n| + 1. \tag*{(242)} Δ n = ∣ n ∣ + 1. (242)
A scalar of dimension Δ n \Delta_n Δ n in global A d S 3 AdS_3 A d S 3 , with angular momentum m m m and radial quantum number p p p , has energy
E A d S 3 = Δ n + ∣ m ∣ + 2 p . (243) E_{AdS_3} = \Delta_n + |m| + 2p. \tag*{(243)} E A d S 3 = Δ n + ∣ m ∣ + 2 p . (243)
Upon using Eq. (241) , we finally obtain the expression for the energy as
E A d S 3 × S 1 = ∣ n ∣ + ∣ m ∣ + 2 p + 1. (244) E_{AdS_3 \times S^1} = |n| + |m| + 2p + 1. \tag*{(244)} E A d S 3 × S 1 = ∣ n ∣ + ∣ m ∣ + 2 p + 1. (244)
which exactly agrees with E S 3 × R E_{S^3 \times\mathbb{R}} E S 3 × R in Eq. (231) .