The replica limit of unitary matrix integrals

We derive Virasoro constraints for the zero momentum part of the QCD-like partition functions in the sector of topological charge $\nu$. The constraints depend on the topological charge only through the combination $N_f +\beta\nu/2$ where the value of the Dyson index $\beta$ is determined by the reality type of the fermions. This duality between flavor and topology is inherited by the small-mass expansion of the partition function and {\em all} spectral sum-rules of inverse powers of the eigenvalues of the Dirac operator. For the special case $\beta=2$ but arbitrary topological charge the Virasoro constraints are solved uniquely by a Generalized Kontsevich Model with potential ${\cal V}(X) = 1/X$.

Multicritical microscopic spectral correlators of hermitian and complex matrices

We examine random matrix models of QCD which are capable of supporting both chiral and diquark condensation. A numerical study of the spectral densities near zero virtuality shows that the introduction of color in the interactions does not alter the one-body results imposed by chiral symmetry. A model with three colors has the spectral density predicted for the chiral ensemble with a Dyson index $\ensuremath{\beta}=2;$ a pseudoreal model with two colors exhibits the spectral density of the chiral ensemble with $\ensuremath{\beta}=1.$

In this paper, we consider characterisations of the class of unitary matrix integrals $\big\langle (\det U)^q {\rm e}^{s^{1/2} \operatorname{Tr}(U + U^\dagger)} \big\rangle_{U(l)}$ in terms of a first-order matrix linear differential equation for a vector function of size $l+1$, and in terms of a scalar linear differential equation of degree ${l+1}$. It will be shown that the latter follows from the former. The matrix linear differential equation provides an efficient way to compute the power series expansion of the matrix integrals, which with $q=0$ and $q=l$ are of relevance to the enumeration of longest increasing subsequences for random permutations, and to the question of the moments of the first and second derivative of the Riemann zeta function on the critical line, respectively. This procedure is compared against that following from known characterisations involving the $\sigma$-Painlevé III$'$ second-order nonlinear differential equation. We show too that the natural $\beta$ generalisation of the unitary group integral permits characterisation by the same classes of linear differential equations.

Recently, Vontobel showed the relationship between Bethe free energy and annealed free energy for protograph factor graph ensembles. In this paper, annealed free energy of any random regular factor graph ensembles are connected to Bethe free energy. The annealed free energy is expressed as the solution of maximization problem whose stationary condition coincides with equations of belief propagation since the contribution to partition function of particular type of variable and factor nodes has similar form of minus Bethe free energy. It gives simple derivation of quenched free energy by using the replica method. It implies equivalence of the replica and cavity methods for any random irregular factor graph ensembles. As consequence, it is shown that the replica symmetric solution and annealed free energy are equal for regular ensemble.

On finite-volume gauge theory partition functions

Two distinct methods for measuring topological charge in a nonabelian anyonic system have been discussed in the literature: projective measurement of a single point-like quasiparticle and interferometric measurement of the total topological charge of a group of quasiparticles. Projective measurement by definition is only applied near a point and will project to a topological charge sector near that point. Thus, if it is to be applied to a group of anyons to project to a total charge, then the anyons must first be fused one by one to obtain a single anyon carrying the collective charge. We show that interferometric measurement is strictly stronger: Any protocol involving projective measurement can be simulated at low overhead by another protocol involving only interferometric measurement.

Two-dimensional Yang-Mills theory is a useful model of an exactly solvable gauge theory with a string theory dual at large N. We calculate entanglement entropy in the 1/N expansion by mapping the theory to a system of N fermions interacting via a repulsive entropic force. The entropy is a sum of two terms: the “Boltzmann entropy,” log dim(R) per point of the entangling surface, which counts the number of distinct microstates, and the “Shannon entropy,” − Σ pR log pR, which captures fluctuations of the macroscopic state. We find that the entropy scales as N2 in the large N limit, and that at this order only the Boltzmann entropy contributes. We further show that the Shannon entropy scales linearly with N, and confirm this behaviour with numerical simulations. While the term of order N is surprising from the point of view of the string dual — in which only even powers of N appear in the partition function — we trace it to a breakdown of large N counting caused by the replica trick. This mechanism could lead to corrections to holographic entanglement entropy larger than expected from semiclassical field theory.

We study the multi-charged moments for two disjoint intervals in the ground state of two 1 + 1 dimensional CFTs with central charge c = 1 and global U(1) symmetry: the massless Dirac field theory and the compact boson (Luttinger liquid). For this purpose, we compute the partition function on the higher genus Riemann surface arising from the replica method in the presence of background magnetic fluxes between the sheets of the surface. We consider the general situation in which the fluxes generate different twisted boundary conditions at each branch point. The obtained multi-charged moments allow us to derive the symmetry resolution of the Rényi entanglement entropies and the mutual information for non complementary bipartitions. We check our findings against exact numerical results for the tight-binding model, which is a lattice realisation of the massless Dirac theory.

We study the dependence of supersymmetric partition functions on continuous parameters for the flavor symmetry group, GF, for 2d mathcal{N} = (0, 2) and 4d mathcal{N} = 1 supersymmetric quantum field theories. In any diffeomorphism-invariant scheme and in the presence of GF ’t Hooft anomalies, the supersymmetric Ward identities imply that the partition function has a non-holomorphic dependence on the flavor parameters. We show this explicitly for the 2d torus partition function, {Z}_{T^2} , and for a large class of 4d partition functions on half-BPS four-manifolds, {Z}_{{mathcal{M}}^4} — in particular, for mathcal{M} 4 = S3 × S1 and mathcal{M} 4 = Σg × T2. We propose a new expression for {Z}_{{mathcal{M}}_{d-1}times {S}^1} , which differs from earlier holomorphic results by the introduction of a non-holomorphic “Casimir” pre-factor. The latter is fixed by studying the “high temperature” limit of the partition function. Our proposal agrees with the supersymmetric Ward identities, and with explicit calculations of the absolute value of the partition function using a gauge-invariant zeta-function regularization.

We provide a formula for the partition function of five-dimensional mathcal{N}=1 gauge theories on ℳ4 × S1, topologically twisted along ℳ4 in the presence of general background magnetic fluxes, where ℳ4 is a toric Kähler manifold. The result can be expressed as a contour integral of the product of copies of the K-theoretic Nekrasov’s partition function, summed over gauge magnetic fluxes. The formula generalizes to five dimensions the topologically twisted index of three- and four-dimensional field theories. We analyze the large N limit of the partition function and some related quantities for two theories: mathcal{N} = 2 SYM and the USp(2N) theory with Nf flavors and an antisymmetric matter field. For ℙ1×ℙ1×S1, which can be easily generalized to {varSigma}_{{mathfrak{g}}_2}times {varSigma}_{{mathfrak{g}}_1}times {S}^1 , we conjecture the form of the relevant saddle point at large N. The resulting partition function for mathcal{N} = 2 SYM scales as N3 and is in perfect agreement with the holographic results for domain walls in AdS7 × S4. The large N partition function for the USp(2N) theory scales as N5/2 and gives a prediction for the entropy of a class of magnetically charged black holes in massive type IIA supergravity.

The partition function of a three-dimensional mathcal{N}=2 theory on the manifold ℳg,p, an S1 bundle of degree p over a closed Riemann surface Σg, was recently computed via supersymmetric localization. In this paper, we compute these partition functions at large N in a class of quiver gauge theories with holographic M-theory duals. We provide the supergravity bulk dual having as conformal boundary such three-dimensional circle bundles. These configurations are solutions to mathcal{N}=2 minimal gauged supergravity and pertain to the class of Taub-NUT-AdS and Taub-Bolt-AdS preserving 1/4 of the supersymmetries. We discuss the conditions for the uplift of these solutions to M-theory, and compute the on-shell action via holographic renormalization. We show that the uplift condition and on-shell action for the Bolt solutions are correctly reproduced by the large N limit of the partition function of the dual superconformal field theory. In particular, the Σg × S1 = ℳg,0 partition function, which was recently shown to match the entropy of AdS4 black holes, and the S3 ≅ ℳ0,1 free energy, occur as special cases of our formalism, and we comment on relations between them.

We study the symmetry resolution of the entanglement entropy of an interval in two-dimensional conformal field theories (CFTs), by relating the bipartition to the geometry of an annulus with conformal boundary conditions. In the presence of extended symmetries such as Kac-Moody type current algebrae, symmetry resolution is possible only if the boundary conditions on the annulus preserve part of the symmetry group, i.e. if the factorization map associated with the spatial bipartition is compatible with the symmetry in question. The partition function of the boundary CFT (BCFT) is then decomposed in terms of the characters of the irreducible representations of the symmetry group preserved by the boundary conditions. We demonstrate that this decomposition already provides the symmetry resolution of the entanglement spectrum of the corresponding bipartition. Considering the various terms of the partition function associated with the same representation, or charge sector, the symmetry-resolved Rényi entropies can be derived to all orders in the UV cutoff expansion without the need to compute the charged moments. We apply this idea to the theory of a free massless boson with U(1) U ( 1 ) , \mathbb{R} ℝ and \mathbb{Z}_2 ℤ 2 symmetry.

We discuss the spectrum of the QCD Dirac operator both at zero and at nonzero baryon chemical potential. We show that, in the ergodic domain of QCD, the Dirac spectrum can be obtained from the replica limit of a Toda lattice equation. At zero chemical potential this method explains the factorization of known results into compact and noncompact integrals, and at nonzero chemical potential it allows us to derive the previously unknown microscopic spectral density.

We study the partition function of a two-dimensional Coulomb gas on a circle, in the presence of external pointlike charges, in a double scaling limit where both the external charges and the number of gas particles are large. Our original motivation comes from studying amplitudes for multi-string emission from a decaying D-brane in the high-energy limit. We analyze the scaling limit of the partition function and calculate explicit results. We also consider applications to random matrix theory. The partition functions can be related to random scattering or to weights of lattice paths in certain growth models. In particular, we consider the discrete polynuclear growth model and use our results to compute the cumulative probability density for the height of long level-1 paths. We also obtain an estimate for an almost certain maximum height.