arXiv:1308.2959v3 [hep-th] 18 Dec 2013 Modular Properties of 3D Higher Spin Theory Wei Li,aFeng-Li Lin,band Chih-Wei Wangb aMax-Planck-Institut f¨ur Gravitationsphysik, Albert-Einstein-Institut, Am M¨uhlenberg 1, 14476 Golm, Germany wei.li@aei.mpg.de bDepartment of Physics, National Taiwan Normal University, Taipei, 116, Taiwan linfengli@phy.ntnu.edu.tw,freeform1111@gmail.com Abstract In the three-dimensionalsl(N) Chern-Simons higher-spin theory, we prove that the conical surplus and the black hole solution are related by the S-transformation of the modulus of the boundary torus. Then applying the modular group on a given conical surplus solution, we generate a ‘SL(2,Z)’ family of smooth constant solutions. We then show how these solutions are mapped into one another by coordinate transformations that act non-trivially on the homology of the boundary torus. After deriving a thermodynamics that applies to all the solutions in the ‘SL(2,Z)’ family, we compute their entropies and free energies, and determine how the latter transform under the modular transformations. Summing over all the modular images of the conical surplus, we write down a (tree-level) modular invariant partition function.
Contents 1Introduction and Summary1 2Basics of 3D higher-spin theory3 2.1Action. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 2.2Asymptotic symmetries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 2.3Smooth solutions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6 3Thermodynamics11 3.1Variational principle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 3.2On-shell action, free energy, and entropy. . . . . . . . . . . . . . . . . . . .17 4Conical surplus and black hole are S-dual21 4.1S-transformation of holonomy condition and on-shell charges . . . . . . . . .22 4.2Coordinate transformation between conical surplus and black hole . . . . . .25 4.3S-transformation of free energies . . . . . . . . . . . . . . . . . . . . . . . . .26 4.4Example-1:N= 3 case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30 5SL(2,Z)family of smooth solutions32 5.1Solution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32 5.2Reasoning from dual CFT. . . . . . . . . . . . . . . . . . . . . . . . . . . .35 5.3Coordinate transformations between members of ‘SL(2,Z)’ family. . . . . .36 5.4Mapping of the free energy . . . . . . . . . . . . . . . . . . . . . . . . . . . .38 5.5Modular invariant full partition function. . . . . . . . . . . . . . . . . . . .40 6Discussion40 6.1Modular invariance of integrability condition . . . . . . . . . . . . . . . . . .41 6.2Canonical vs. holomorphic . . . . . . . . . . . . . . . . . . . . . . . . . . . .43 ASolvingσsin terms ofµs44 BSL(2,Z)family in spin-2case45 CExample-2:N= 446 1Introduction and Summary In the theory of the three-dimensional pure Einstein gravity with a negative cosmological constant, as there is no propagating degree of freedom in the bulk, all asymptotically AdS so- lutions are locally diffeomorphic and differ only in their global structures [1–4]. In Euclidean signature, starting with a thermal AdS3, whose conformal boundary is a torus with modulus τ, we can obtain an ‘SL(2,Z)’ family of solutions via modular transformations (τ7→aτ+b cτ+d) on the modulus of the boundary torus [5]. In particular, the S-transformationτ7→ −1 τmaps 1
the AdS3into a BTZ black hole. The full modular invariant partition function consists of a sum of all the modular images of the AdS3partition function:Z[τ] =∑ZAdS3[aτ+b cτ+d] [6]. One can then study the phase structure usingZ[τ], and for example show how Hawking- Page transition [7] occurs whenτmoves across the boundary between different fundamental domains [5, 6, 8]. Vasiliev’s higher-spin theory is a generalization of the gravity theory; besides the gravi- ton, it contains massless spin-sfields withs≥3; and it lives in spaces with non-zero constant curvatures, i.e. AdS or dS spaces [9–12]. In three dimensions, it can be consistently trun- cated to a Chern-Simons subsector after the scalar in the theory is decoupled [13, 14].1We only consider AdS space in this paper.In AdS3, the gauge algebra of this Chern-Simons theory is an infinite-dimensional Lie algebra hs[λ] [15, 16], which atλ=Nreduces to the finite-dimensionalsl(N) [9, 17]. The 3D Chern-Simons high-spin theory is a straightforward generalization of thesl(2) Chern-Simons theory (the alternative formulation of the 3D pure gravity with a negative cosmological constant [18,19]) and share its essential features: in par- ticular, it does not have any propagating degree of freedom in the bulk of the three-manifold M; the topology ofMand the boundary data on∂Mdetermine the dynamics. In the Chern-Simons higher-spin theory, two types of smooth solutions have been found and studied: the conical surplus constructed by [20] and the black hole by [21]. They can be viewed as the higher-spin-charge-carrying generalizations of the AdS3and BTZ black hole, respectively. Since the notion of the boundary torus still exists in the higher-spin version of the Chern-Simons theory, we can ask whether these two solutions, the conical surplus and the black hole, are related via an S-transformation of the modulus of the boundary torus. In some sense, this has to happen since these two solutions reduce to AdS3and BTZ when all the higher-spin charges are set to zero.The non-trivial part of the story is this: the boundary modulusτcan be considered as the thermodynamical conjugate of the spin-2 charge, and in the higher-spin theory, the spin-2 field is coupled with all the higher-spin fields, therefore a transformation ofτinevitably induces the corresponding transformations on the chemical potentials of all the higher-spin charges.The crux in generalizing the modular properties of the spin-2 theory to a higher-spin theory is in determining this induced transformations on the higher-spin chemical potentials. For this purpose, one first needs a consistent description of the thermodynamics of the given solution. Up till now this is absent for the conical surplus; however for the black hole an extensive literature on its thermodynamics has already emerged:e.g.a ‘holomorphic’ approach represented by [21–26] and a ‘canonical’ one represented by [27–29]. In this paper we choose the ‘canonical’ formalism because, as we will show later, in this formalism important quantities and equations are manifestly modular invariant or covariant. 1In 3D, the scalar does not sit in the higher-spin multiplet therefore can be consistently decoupled. 2
In the ‘canonical’ formalism we generalize the thermodynamics of the black hole to include all smooth stationary solutions. Once the thermodynamics of the conical surplus is established, we determine the required transformation on the higher-spin chemical potential accompanying the S-transformation on the boundary modulusτ7→ −1 τ, and prove that the conical surplus and the black hole are S-dual. We then show that the black hole and the conical surplus are related by a coordinate transformation (that changes the modular parameter of the boundary torus fromτto−1 τ). Then we generalize from the S-transformation to the full modular group: starting with a higher-spin-charge-carrying conical surplus solution and applying on it the full modular group, we can generate an ‘SL(2,Z)’ family of smooth stationary solutions. They are all con- nected by coordinate transformations that act non-trivially on the homology of the boundary torus.Their free energies hence their on-shell partition functions are related via modular transformations. The full modular invariant partition function then involves summing over all the modular images of the conical surplus. The paper is organized as follows. In Section 2 we briefly review some basics of 3Dsl(N) higher-spin theory, summarize known stationary smooth solutions, and define new smooth stationary solutions in the ‘SL(2,Z)’ family. In Section 3 we formulate a thermodynamics that is universal to all members of the ‘SL(2,Z)’ family (including conical surplus and black hole). Then in Section 4 we prove that a conical surplus can be mapped into a black hole via an S-transformation of the modulus of the boundary torus. In section 5 we show how to generate an ‘SL(2,Z)’ family of smooth solutions. We summarize and discuss open problems in section 6. In Appendix A we present a detailed proof for a statement that is central to our paper; in Appendix B we review the spin-2 story; finally in Appendix C we discusssl(4) theory as a concrete example. 2Basics of 3D higher-spin theory In this section we first review some basics of the three-dimensionalsl(N) higher-spin theory (for more details see the earlier works [20,21,30] and the reviews [31,32]). Then we summarize known smooth solutions in this theory, i.e.the conical surplus and the black hole, and meanwhile prepare the readers for our later discussion on general smooth solutions. In this paper we focus on stationary, axially symmetric, solutions. 3
2.1Action In three dimensions, the Einstein-Hilbert action with a negative cosmological constant Λ can be rewritten in terms of ansl(2,R)⊕sl(2,R) Chern-Simons theory (up to a boundary term) [18, 19]: S=SCS[A]−SCS[ ¯A]withSCS[A] =k 4π ∫ M Tr[A∧dA+ 2 3A∧A∧A](2.1) whereMis a locally AdS3manifold;Aand¯Aaresl(2,R) gauge fields; the trace ‘Tr’ is on the 2-dimensional representation ofsl(2) and the levelk=lAdS3 4GN.This trick (of rewriting Einstein-Hilbert action with a negative Λ into a gauge theory) only works in three dimensions. On the other hand, the three-dimensional Vasiliev higher-spin theory is also much more tractable than its higher-dimensional siblings. Besides the gauge fields, the theory has only one additional scalar field, which can be consistently decoupled since it is not part of the higher-spin multiplet in 3D. The gauge field subsector can then be written as a Chern-Simons theory (2.1) withAand ¯A∈hs[λ], which is an infinite-dimensional Lie algebra and atλ=N reduces tosl(N) (after quotiented by an infinite ideal). In this paper we will focus on the 3Dsl(N) Chern-Simons theory. The trace ‘Tr’ in the Chern-Simons action (2.1) is now on theN-dimensional representation ofsl(N) and the level becomesk=ℓAdS 4GN 1 2 Tr[(L0)2].2 Now let us parametrize the base manifoldM. Since the theory has a negative cosmologi- cal constant, we choose the boundary condition to be asymptotically AdS3. A constant-time slice of an asymptotically AdS3spaceMis topologically a disc. Specify a radial coordinate ρand an angular coordinateφ, the coordinate is then{ρ, t, φ}. The asymptotic boundary ∂Mis atρ→ ∞and the boundary coordinates are{t, φ}. In this paper, we focus on Euclidean signature. The Wick rotation into Euclidean signa- ture is viat7→itEand the coordinate becomes{ρ, z,¯z}with z≡φ+itE.(2.2) Accordingly, the gauge symmetry becomessl(N,C). The connectionA∈sl(N,C); and in the representation we will choose, ¯AisA’s anti-hermitean conjugate:3 ¯A=−A†.(2.3) Therefore, most of the time we only need to write theA’s side of the expression and the one 2This additional normalization factor1 2 Tr[(L0)2]is necessary for the spin-2 subsector ofsl(N) higher-spin theory to match the Einstein gravity. 3This is also the convention used by [20, 27, 33] 4
for ¯Acan then be inferred using (2.3). The Chern-Simons action (2.1) has gauge degrees of freedomA∼A+dΛ, which allows us to fix the gauge as: A(ρ, z,¯z) =b−1a(z,¯z)b+b−1db(2.4) whereb=eρL0is an SL(N)-valued 0-form, andais ansl(N)-valued 1-form on the boundary ∂M: a=azdz+a¯zd¯z .(2.5) 2.2Asymptotic symmetries Thesl(2) subalgebra corresponds to the spin-2 (i.e. gravity) sector, with generators{L0,±1}, whose commutators are: [Lm, Ln] = (m−n)Lm+n,m, n=−1,0,1.(2.6) (We will also sometimes writeLn=W(2) n.) From thesl(N) gauge symmetry, we first need to make a choice as to whichsl(2) subalgebra corresponds to the gravity sector, namely we need to choose how the gravitysl(2) embeds in the full gauge algebrasl(N).The choice of this embedding then determines the spectrum of the theory.The principal embedding is particularly simple because the field of each spin appears once and only once.In this paper we only discuss the principal embedding and a generalization to other embeddings is straightforward. Next, one can choose the boundary condition forAand determine the asymptotic sym- metry group. This was done in [30, 34–36]. In the absence of sources, the asymptotic AdS condition implies A¯z= 0.(2.7) However this boundary condition (2.7) is too weak and gives rise to a phase space that is too large (with an affinesl(N) algebra as its asymptotic symmetry).An additional boundary condition was proposed by [30] to supplement (2.7) (see also [37] for the spin-2 case): (A−AAdS)|ρ→∞=O(1),(2.8) which reduces the phase space by imposing a first-class constraint on thesl(N) affine algebra and results in aWNalgebra as the asymptotic symmetry. This is the bulk realization of the Drinfeld-Sokolov reduction (the reduction of an affine algebra to aW-algebra) [38]. 5
In the process of the Drinfeld-Sokolov reduction, different gauge choices give different bases for theW-algebra. A particular convenient choice is the highest-weight gauge, which gives rise to aW-algebra in which allW(s)are primaries with respect to the lowest spins [30,36]. Since there is no spin-1 field in thesl(N) Chern-Simons theory, allW(s≥3)fields are Virasoro primaries: [Lm, W(s) n]=[(s−1)m−n]W(s) m+n,s= 3, . . . , N ,m, n∈Z.(2.9) This is the gauge we will use throughout this paper.4 Recall that in the spin-2 case the bulk isometrysl(2) is given by the ‘wedge’ subalgebra (generated byL−1,0,1) of Virasoro algebra.Here the (N2−1)-dimensional bulk isometry sl(N) is generated byW(s) mwiths= 2, . . . , Nandm=−s+ 1, . . . , s−1.An explicit representation of (2.9) form≤ |N|is [39]: W(s) n= (−1)s−n−1(s+n−1)! (2s−2)!(AdjL−1)s−n−1(L1)s−1(2.10) where the adjoint action AdjAB= [A, B]. Lastly, we will choose a convention in which (Lm)†= (−1)mL−m(2.11) which together with (2.10) implies (W(s) m)†= (−1)mW(s) −mfors= 2, . . . , N. In this convention we have (2.3). 2.3Smooth solutions 2.3.1Equations of motion The equation of motion of the Chern-Simons action is the flatness condition forA:F≡ dA+A∧A= 0. In the gauge (2.4), this translates into the flatness ofa: f≡da+a∧a= 0.(2.12) In this paper we will only consider axially-symmetric, stationary, solutions.For these solutions,Ahas onlyρ-dependence. In the gauge (2.4) , this means thatais constant, hence throughout this paper we will refer to them as constant solutions (although they can rotate). 4Other gauges are possible and might be more suitable for other questions, for details see [36]. 6
Their equations of motion (2.12) reduce to [az, a¯z] = 0.(2.13) Onceazis fixed,a¯zcan be determined via the equation of motion (2.13), whose solution is simplya¯zbeing an arbitrary traceless function ofaz.By Cayley-Hamilton theorem, an arbitrary function of aN×Nmatrixaz(that is generic enough) truncates to a polynomial ofazof degree-(N−1); thereforea¯zhas the expansion [51]: a¯z= N∑ s=2 σs [ (az)s−1−Tr(az)s−1 N1 ] .(2.14) Up to now,{σs}are (N−1) arbitrary complex parameters. Later we will show how they are fixed in terms of the chemical potentials of the higher-spin charges. 2.3.2Holonomy condition In this subsection, we define the condition that characterizes a generic smooth constant solution.The known solutions, i.e.the conical surplus and the black hole, are the two special cases. Any givenaztogether with thea¯zrelated by it via (2.14) would solve the equation of motion (2.13). However, requiring the solution be smooth imposes a much more stringent constraint.Since in the higher-spin theory, the spin-2 field is coupled with all higher-spin fields hence the Ricci scalar is no longer a gauge invariant entity, the smoothness condition need to be prescribed in terms of other, gauge-invariant, observables.In the 3D Chern- Simons theory, the natural candidate is the holonomy around a one-cycleCinM: HolC(A)≡ Pe∮ CA.(2.15) The smoothness condition is then simply that the holonomy around any contractible cycle (A-cycle) must be trivial, i.e. HolA(A)∈center of the gauge group [20, 21]. First let us describe the cycles in this 3D Euclidean spacetime. The asymptotic boundary of the Euclidean AdS3is a torus. First we fix its homology basis (α, β) withα∩β= 1. Then we give this torus a complex structure. This allows us to define a holomorphic 1-formω; we can choose its basis such that∮ αω= 1, thenτ≡∮ βωdefines the modulus of the torus. Once the modulus of the boundary torus is fixed, different bulk geometries correspond to different ways of filling the solid torus.We first fix the primitive contractible cycle (A-cycle), then the primitive non-contractible cycle (B-cycle) that satisfies A∩B= 1 is uniquely determined up to shifts in the A-cycle. The (A,B) homology basis is related to the original (α, β) basis 7
via a modular transformation: ( B A ) = ( ab cd ) ( β α ) with ( ab cd ) ∈PSL(2,Z)(2.16) with PSL(2,Z)≡SL(2,Z)/Z2,SL(2,Z)≡ { ( ab cd ) ∣ ∣a, b, c, d∈Z, ad−bc= 1}.(2.17) Then the torus with (A,B) as the homology basis but with the same holomorphic 1-formω has a modular parameter modular parameter≡ ∫ Bω ∫ Aω=aτ+b cτ+d ,(2.18) which is a modular transformation of the original modulusτ.Throughout this paper, we useγto denote an element of the modular group PSL(2,Z) and define ˆγτto be its action onτ:5 γ≡ ( ab cd ) ∈PSL(2,Z) :τ7−→ˆγτ≡aτ+b cτ+d .(2.19) Also note that throughout this paper, bymodular parameterwe mean the ratio of the (complex) length of the non-contractible(B) cycle and that of the contractible(A) cycle, as defined in (2.18); and we reserve the termmodulusforτ. The conical surplus solutions that carry higher-spin charges has a contractible cycle φ∼φ+ 2π, just like the AdS3[20]. CS:γ= ( 10 01 ) =⇒A-cycle:z∼z+ 2π , B-cycle:z∼z+ 2πτ .(2.20) Accordingly, the holonomy around thisφ-cycle needs to lie in the center of the gauge group: Holφ(A) =b−1e2πωφb∈center ofG(2.21) whereωφis defined as6 ωφ≡az+a¯z.(2.22) 5In PSL(2,Z),γand−γare identified, hence we can choosec≥0 without loss of generality. 6Throughout the paper we will call suchω‘holonomy matrix’. 8
Let’s denote by ‘Λ (ω)’ the vector of eigenvalues of a matrixω: U ω U−1= DiagonalMatrix[λ1, . . . , λN]=⇒Λ (ω)≡~λ= (λ1, . . . , λN).(2.23) The center of SL(N,C) ise−2πim N1withm∈ZN, which implies that the eigenvalues ofωφ satisfies [20]: Λ (ωφ) =i ~n ,(2.24) where the vector~n= (n1, . . . , nN) withni∈Z−m N,ni6=njfori6=j, and∑N ini= 0, and most importantlynimust come in pairs for the solution to be a conical surplus, i.e. if we order{ni}into a monotone sequence then ni+nN+1−i= 0.(2.25) This imposes a very strong constraint onm:m= 0 forNodd, andm= 0 orN 2forNeven. But recall that the center of SL(N,R) is precisely1forNodd and±1forNeven;7therefore the constraint (2.25) forces the holonomy to lie in the center of the Lorentzian gauge group SL(N,R) rather than that of the Euclidean one SL(N,C). In summary the vector~nobeys ~n= (n1, . . . , nN),ni∈ ZNodd ZorZ+1 2Neven ,ni6=njfori6=j ,ni+nN+1−i= 0, (2.26) and can be considered as a ‘topological charge’ of the solution; and we will term it ‘holonomy vector’.The global AdS3space corresponds to~n=~ρ(the Weyl vector ofsl(N), with ρi=N+1 2−i), and generic~n’s satisfying (2.26) give conical surpluses [20]. For discussions on the conical surplus in hs[λ] Chern-Simons theory see e.g. [40–45] On the other hand, the (Euclidean) black hole has a contractible cyclez∼z+ 2πτ. BH:γ= ( 0−1 10 ) =⇒A-cycle:z∼z+ 2πτ , B-cycle:z∼z−2π .(2.27) Accordingly, the trivial holonomy condition is [21]: Holt(A) =b−1e2πωtb∈center of SL(N,R),(2.28) withωtdefined as ωt≡τ az+ ¯τ a¯z.(2.29) 7The±1forNeven arises from the fact that the gauge group is actually (SL(N,R)/Z2)×(SL(N,R)/Z2) [20]. 9
Namely Λ (ωt) =i ~n ,(2.30) with~nsatisfying the same set of conditions as the conical surplus (2.26).~n=~ρcorresponds to the higher-spin-charge-carrying BTZ black hole first constructed in [21]; and other~n’s give more generic higher-spin black holes. This definition of smooth solution by the holonomy around the contractible cycle can be easily generalized to include solutions whose modular parameter is a generic ˆγτ(other than τor−1 τ). For a genericγ= (ab cd ) ∈PSL(2,Z), the A/B cycles are Contractible(A)-cycle:z∼z+ 2π(cτ+d), Non-contractible(B)-cycle:z∼z+ 2π(aτ+b).(2.31) Accordingly, for a smooth solution, the holonomy around the A-cycle should be trivial HolA(A) =b−1e2πωAb∈center of SL(N,R),(2.32) with the holonomy matrix around the A-cycle given by ωA≡1 2π ∮ A a= (cτ+d)az+ (c¯τ+d)a¯z,(2.33) namely Λ (ωA) =i ~n(2.34) again with~ngiven by (2.26).Here we also write down the holonomy matrix around the B-cycle for comparison and for later use: ωB≡1 2π ∮ B a= (aτ+b)az+ (a¯τ+b)a¯z.(2.35) For given~nandτ, varyingγ∈PSL(2,Z) then generates a ‘SL(2,Z)’ family of solutions (a term coined in [5]). Since the T-transformationτ7→τ+ 1 does not change the A/B cycle (2.31), we should consider the subgroup of Γ≡PSL(2,Z) Γ∞≡ { ( 1m 01 ) ∣ ∣m∈Z}/Z2⊂Γ≡PSL(2,Z).(2.36) to be the stabilizer; hence the ‘SL(2,Z)’ family is actually the quotient Γ∞\Γ.Since aγ in Γ∞\Γ is uniquely given by the lower row (c, d) (which always satisfies gcd(c, d) = 1), an 10
enumeration of all the members in this family is thus [46]: ∀(c, d)withc, d∈Z,c≥0,gcd(c, d) = 1.(2.37) Lastly, the holonomy vector for ¯Ais always related to that ofAvia ~¯n=~n(2.38) in the anti-hermitean basis we choose.We summarize the discussion of this subsection in the following table: EAdS3and CSblack holeSmooth solutionγ A-cyclez∼z+ 2πz∼z+ 2πτz∼z+ 2π(cτ+d) B-cyclez∼z+ 2πτz∼z−2πz∼z+ 2π(aτ+b) modular parameterτ−1 τ aτ+b cτ+d A-cycle holonomyωφ=az+a¯zωt=τ az+ ¯τ a¯zωA= (cτ+d)az+ (c¯τ+d)a¯z 3Thermodynamics The conical surplus solution constructed in [20] has higher-spin charges but with no chemical potential turned on, and hence there is no study on its thermodynamics yet. Meanwhile, the thermodynamics of the black hole in thesl(N) Chern-Simons theory has been extensively studied, and depending on the choice of the spin-2 conserved charge (the zero-mode of the energy-momentum tensor) there are two main approaches. In the ‘holomorphic’ formalism (initiated in [21] and used in [22–26]), the spin-2 conserved charge (for the left-moverA) Tis holomorphic.8In the ‘canonical’ formalism, the spin-2 conserved chargeTis obtained either via a canonical approach [28, 29] `a la Regge-Teitelboim [50], or via a direct derivation from the variational principle [27] (for a precursor see [51]) which gives the same result; in this formalismTis not holomorphic and receives contribution from the right-mover ¯A. The different definitions of (T,¯T) in turn leads to different results for the integrability condition, the entropy, and finally the free energy.For more details see the discussion in [27].(For other discussions on the black hole thermodynamics see [52, 53].) Now we would like to generalize the result of the thermodynamics of the black hole to the conical surplus and to all smooth constant solutions in the ‘SL(2,Z)’ family. Which of the two formalism is better suited for this purpose? Usually the modularity (w.r.t. PSL(2,Z)) 8For the CFT computation in this formalism see [47–49]. 11
requires the holomorphicity of the theory.Therefore naively one would expect that the ‘holomorphic’ formalism be the choice whereas the modular property be absent or at least obscured in the ‘canonical’ formalism. However, the fact that in the ‘canonical’ formalismTlacks holomorphicity therefore modularity does not pose any problem in a discussion of the modular properties in this formalism.First of all, although the spin-2 conserved chargeT, and hence the entropy, is not modular covariant, this is to be expected since they are not holomorphic to start with.Moreover they are only intermediate quantities.As we will show presently, all the other final quantities — the connection, the holonomy condition, and the free energy — are modular invariant or covariant. We will derive manifestly modular covariant expressions for them.We will also show later in Section 6 that the crucial consistency condition — the integrability condition (relating conserved charges of different spins) — is modular invariant in the ‘canonical’ formalism. On the other hand, as we will discuss in Section 6, in the ‘holomorphic’ formalism, it is not clear to us how to write down a simple modular transformation such that the various important relations — the holonomy condition, the integrability condition, etc — are modular invariant or covariant. This leads us to choose the ‘canonical’ formalism developed in [27] for our generalization of thermodynamics of the black hole to all members of the ‘SL(2,Z)’ family. In this section, we generalize the procedure in [27, 51] 1. Vary the bulk action and identify the source and charge terms in the connection. 2. Write down the suitable boundary action to ensure the variational principle. 3. Identify the conjugate pair of energy and temperature, compute the free energy and entropy, and check the first law of thermodynamics. to generic smooth constant solutions (including the conical surplus). In particular, we com- pute the on-shell action for generic solutions and write down the modular covariant expres- sions for the entropy and free energy. One clarification: the construction of these general smooth constant solutions will only be shown later, in Section 5. However, since we first need to know the thermodynamics of the conical surplus solution (in order to consistently turn on its chemical potentials) before we can discuss its relation with the black hole solution, and since the thermodynamics of all these smooth solutions can be discussed in an unified way (and with no need to know the full details of the solutions), we will study all of them at once now, and postpone the explicit construction of these solutions to Section 5. 12
3.1Variational principle In the presence of higher-spin conserved chargesQswiths= 3, . . . , N, the partition function (evaluated as an Euclidean path-integral) is a function of the boundary modulusτand the chemical potentialµsconjugate to the higher-spin chargeQs: Z[τ;µs]≡ ∫ DAD¯A e−I(E) (3.1) The free energy of the system is −βF[τ;µs] = lnZ[τ;µs].(3.2) In this paper, we take the saddle point approximation (i.e. only include the classical result): each classical solution contributese−I(E)|on-shell. For each classical solution, its free energyF (in the saddle point approximation) is given by −βF=−I(E)|on-shell.(3.3) In this section, we study the on-shell action of individual solutions; we will discuss the contributions from all saddle points to the partition function later in Section 5. 3.1.1Variation of bulk action For the discussion in this section, it is enough to know that a smooth constant solution can be defined by the condition that its holonomy around the A-cycle is trivial, i.e.equation (2.31), (2.32), and (2.34); and it is determined by the PSL(2,Z) elementγ. The thermodynamics for the case ofγ= (0−1 10 ) (the higher-spin black hole with modular parameter−1 τ) was already given in [27].We now generalize its derivation to the generic smooth solution with modular parameterγ= (ab cd ) . The thermodynamical relation comes out of a direct variational calculation of the Chern-Simons action, which tells us how to add the boundary term once the choice of source/field is made. In this variational calculation, the modulus of the boundary torus should actively vary since it carries the physical information of the inverse temperature (and the twist along the angular direction) [27, 56]. However, in the coordinate system (z,¯z) which we have been using, the modular parameter ˆγτis hidden in the identification of the A/B cycle; to make it appear explicitly we need to first switch to a coordinate system (w,¯w) that lives on a rigid torus with fixed modulusτ=i.The coordinate transformation from (z,¯z) to (w,¯w) is z= (cτ+d)(1−iˆγτ 2w+ 1 +iˆγτ 2¯w)(3.4) 13
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Or try the Coinbase Wallet browser extension
Connect with dapps with just one click on your desktop browser
Add an additional layer of security by using a supported Ledger hardware wallet