arXiv subjects

Hewei Frederic Jia

Publications and source records attributed to Hewei Frederic Jia.

6 recordsLinked to original sources

arXiv2026

Exact holographic thermal spectral functions: OPE, non-perturbative corrections, and black hole singularity

We study analytic properties of thermal spectral functions of holographic CFTs, examining both their (a) exact properties at finite momentum and (b) asymptotics at large momentum. For even-dimensional holographic CFTs on Minkowski spacetime and for scalar primaries with integer dimensions, we demonstrate that the exact spectral function at finite momentum factorizes into a perturbative/OPE piece and a non-perturbative piece. The former is controlled by stress tensor exchange and fixed by a near-boundary analysis. The latter encodes information about the bulk interior, including the black hole horizon and singularity. Utilizing the exact factorization, we obtain the full transseries expansion of the non-perturbative piece at large timelike momentum. This is achieved by employing exact WKB techniques to compute the monodromy of the bulk wave equation. Finally, we use these results to work out the singular loci of a spatially averaged thermofield double correlator in the complex time plane. These singular loci have been argued to provide imprints of the black hole curvature singularity in the dual CFT observables. Our result, which includes the case of non-vanishing momentum, gives a clear link between the non-perturbative spectral function and the black hole singularity.

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arXiv2026

Thermal spectral function asymptotics and black hole singularity in holography

We investigate the analytic structure of thermal spectral function of holographic CFTs, synthesizing recent developments into a set of observations about its asymptotics. Specifically, for a class of scalar primaries with integral dimension, we demonstrate factorization of the exact spectral function into a polynomial piece, which captures the vacuum dynamics, and a non-perturbative piece, which controls its asymptotics. Using exact WKB techniques, we derive a transseries expression for the latter. We use this information to deduce the singular loci of a spatially averaged thermofield double correlator in the complex time plane. Such singularities have been argued to encode information regarding the black hole singularity in the dual spacetime. Our results give a refinement of these statements by capturing the momentum dependence.

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arXiv2024

Holographic thermal correlators and quasinormal modes from semiclassical Virasoro blocks

Motivated by its relevance for thermal correlators in strongly coupled holographic CFTs, we refine and further develop a recent exact analytic approach to black hole perturbation problem, based on the semiclassical Virasoro blocks, or equivalently via AGT relation, the Nekrasov partition functions in the Nekrasov-Shatashvili limit. Focusing on asymptotically $\text{AdS}_5$ black hole backgrounds, we derive new universal exact expressions for holographic thermal two-point functions, both for scalar operators and conserved currents. Relatedly, we also obtain exact quantization conditions of the associated quasinormal modes (QNMs). Our expressions for the holographic $\text{CFT}_4$ closely resemble the well-known results for 2d thermal CFTs on $\mathbb{R}^{1,1}$. This structural similarity stems from the locality of fusion transformation for Virasoro blocks. We provide numerical checks of our quantization conditions for QNMs. Additionally, we discuss the application of our results to understand specific physical properties of QNMs, including their near-extremal and asymptotic limits. The latter is related to a certain large-momentum regime of semiclassical Virasoro blocks dual to Seiberg-Witten prepotentials.

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arXiv2023

Twist operator correlators and isomonodromic tau functions from modular Hamiltonians

We introduce a novel approach for computing the twist operator correlators (TOC) in two-dimensional conformal field theories (2d CFT) and the closely related isomonodromic tau functions. The method stems from the formal path integral representation of the ground state reduced density matrix in 2d CFT, and exploits properties of the associated modular Hamiltonians. For a class of genus-zero TOC/tau functions associated with branched covers with non-abelian monodromy group, we present: i) a determinantal representation derived from the correlation matrix method for free fermions, and ii) a formal integral representation derived from the universal single-interval modular Hamiltonians. For the class of genus-zero TOC/tau functions, we also argue an approximate factorization property, utilizing the known ground state correlation structure of large-$c$ holographic CFT and the universality of genus-zero TOCs. We provide explicit examples for verifying the determinantal representation and the approximate factorization property.

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arXiv2023

Twist operator correlator revisited and tau function on Hurwitz space

Correlation function of twist operators is a natural quantity of interest in two-dimensional conformal field theory (2d CFT) and finds relevance in various physical contexts. For computing twist operator correlators associated with generic branched covers of genus zero and one, we present a generalization of the conventional stress-tensor method to encompass generic 2d CFTs without relying on any free field realization. This is achieved by employing a generalization of the argument of Calabrese-Cardy in the cyclic genus zero case. The generalized stress-tensor method reveals a compelling relation between the twist operator correlator and the tau function on Hurwitz space, the moduli space of branched covers, of Kokotov-Korotkin. This stems from the close relation between stress-tensor one-point function and Bergman projective connection of branched cover. The tau function on Hurwitz space is in turn related to the more general isomonodromic tau function, and this chain of correspondence thus relates the twist operator correlator to a canonical algebro-geometric object and endows it with an integrable system interpretation. Conversely, the tau function on Hurwitz space essentially admits a CFT interpretation as the holomorphic part of the twist operator correlator of $c=1$ free boson.

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arXiv2020

Petz reconstruction in random tensor networks

We illustrate the ideas of bulk reconstruction in the context of random tensor network toy models of holography. Specifically, we demonstrate how the Petz reconstruction map works to obtain bulk operators from the boundary data by exploiting the replica trick. We also take the opportunity to comment on the differences between coarse-graining and random projections.

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