Near-extremal dynamics away from the horizon

• Ioannis Papadimitriou (National and Kapodistrian University of Athens (GR))

Near-extremal black holes are usually studied by zooming into the throat that describes their near-horizon geometry. Within this throat, one can argue that two-dimensional JT gravity is the appropriate effective theory that dominates at low temperature. In this talk, I will discuss how to capture this effective description for asymptotically AdS$_{d+1}$ near-extremal black holes purely within the dual UV CFT$_{d}$ at the boundary of AdS$_{d+1}$. This is achieved by identifying the CFT$_{d}$ phase space within the AdS$_{d+1}$ gravitational theory and formulating the decoupling limit directly on this phase space. A key requirement for this construction is that the CFT$_{d}$ phase space identification within the gravity theory holds for all values of the radial coordinate and not merely asymptotically. This requirement is satisfied for Einstein gravity and Topologically Massive Gravity in AdS$_{3}$, as well as for algebraically special solutions in AdS$_{4}$, which are the cases we focus on.

Quantum black hole cohomologies

• Seok Kim

I will discuss the 1-loop lifts of some classical supercharge cohomologies for the 1/16-BPS black hole microstates in AdS5 x S5. I will also discuss by how much the classical cohomologies over-estimate the entropy of absolutely protected 1/16-BPS states in the Cardy limit.

Supertranslations and the Physics of Flat-Bands

• Aritra Banerjee

Log corrections to near-extremal entropy of de Sitter black holes

• Debangshu Mukherjee

I will briefly review logarithmic corrections to black hole entropy. Following that, I will focus on thermodynamics of de Sitter black holes and our recent work (https://arxiv.org/abs/2503.08617) on log T corrections to the entropy of de Sitter black holes. I will establish the result that at leading order, the small temperature corrections to the extremal entropy are universal in the cold and Nariai limit. In particular, in the Nariai limit, the near-horizon throat geometry is 2-dimensional de Sitter space with two possible ways of capping the geometry -- the usual Hartle-Hawking contour and the Maldacena contour, both leading to the same universal coefficient of 3/2 for log T correction to the entropy of de Sitter black holes. This machinery paves the way for similar such computations and tests in higher dimensional dS black hole spacetimes, including rotating Kerr-dS black holes.

Anomaly Induced Current in Boundary Lifshitz Field Theory

• Himanshu ‍Parihar (Kyung Hee University)

We study quantum transport phenomena induced by anisotropic Lifshitz scale anomaly in a boundary Lifshitz field theory (BLFT) coupled to an external electromagnetic background. In this context, we obtain the anisotropic scale anomaly in Lifshitz field theories coupled to a background U(1) gauge field and subsequently compute the anomaly induced near boundary current in a BLFT. Focusing on 5D BLFTs, we find that the temporal and spatial components of the induced current exhibit distinct power law dependencies on the distance from the boundary, reflecting the intrinsic time-space anisotropy of the theory. We further derive this anomalous current holographically from the bulk dual of BLFT and find that the temporal component is independent of the boundary conditions while the spatial component depends explicitly on them. The distance dependence is in exact agreement with the dual field theory result.

Attractor mechanism : Trio of effective black hole potential, entropy functional and Routhian

• Sourav Roychowdhury (Department of Physics & Center for Quantum Spacetime, Sogang University)

In this talk we discuss various aspects of the effective dynamics of Maxwell-Einstein scalar theories in the background of static, spherically symmetric and extremal black hole solution in (1+3) dimensions. We show that the effective one dimensional action (governed by the Attractor mechanism) from which the effective black hole potential (introduced by Ferrara-Gibbons-Kallosh) is usually computed, is the one dimensional effective Routhian of the original (1+3)d action. We further discuss the interplay of this Routhian framework, black hole potential and Sen's entropy functional approach, enabling one to compute the black hole entropy.

Type IIB supergravity and Holography

• Soumya Adhikari

In the AdS/CFT correspondence, holographic observables such as the free energy are typically compared with the Euclidean on-shell action of lower-dimensional gauged supergravity. From a first-principles perspective, however, these quantities should arise directly from the ten-dimensional Type IIB supergravity on-shell action in the leading order. A longstanding puzzle is that the Type IIB pseudo-action evaluated on the $AdS_5 \times S^5$ solution vanishes, apparently obstructing a direct holographic derivation. A recent proposal by Kurlyand and Tseytlin resolves this issue within the Pasti--Sorokin--Tonin (PST) formulation of Type IIB supergravity by introducing an additional topological boundary term, yielding a non-vanishing on-shell action consistent with the holographic result. This construction, however, was originally established only for a restricted class of backgrounds, notably the $AdS_5 \times S^5$ solution with vanishing two-form fields. In this talk, I revisit and extend this framework to a broader class of Type IIB backgrounds relevant for holography. In particular, I analyze geometries of the form $AdS_5 \times M_5$, including both the canonical $S^5$ compactification and deformed solutions such as the Lunin--Maldacena background, as well as more general configurations of the type $AdS_4 \times M_6$. By introducing a generalized topological correction to the ten-dimensional action under milder assumptions, allowing, in particular, for non-vanishing two-form potentials, I demonstrate that the resulting ten-dimensional on-shell actions precisely reproduce the corresponding lower-dimensional gauged supergravity results.

Gravitational charges and radiation in de Sitter

• Kostas Skenderis

I will present a first principles rigorous derivation of gravitational charges in de Sitter using (suitably adapted version of) Noether’s theorem, and show that they satisfy a flux-balance law. The variational problem in de Sitter gravity requires that one specifies a conformal class up to diffeomorpshisms at future and past infinity. Gravitational radiation is possible only when the conformal class is non-trivial. I will illustrate the discussion with several exact solutions, including the radiative Robinson-Trautman-dS solution, which I will use to demonstrate the existence of conserved charges even in the absence of asymptotic (conformal) Killing vectors, and also the existence of monotonic charges, charges that are not conserved but rather change monotonically under time evolution (an example of a monotonic change is the Bondi mass).

Giant Gravitons and Volume Minimisation for Black Hole Horizons

• Nicholas Dorey

Semiclassical Einstein equations and instability from holography

• Akihiro Ishibashi

In this talk, we first discuss how to formulate the semiclassical Einstein equations in the context of holography. Then, as an application of these holographic equations, we examine the dynamical and thermodynamical instabilities of maximally symmetric (i.e., Minkowski, de Sitter, and AdS) spacetimes in d=3, 4, 5 which are also solutions to the holographic semiclassical Einstein equations. We introduce two parameters; one is an effective mass-squared appearing in the perturbation equations, and the other is a dimensionless constant consisting of the bulk and boundary Newton couplings. We then show that depending on the values of these constants, the maximally symmetric spacetimes can be unstable due to the effects of the quantum stress-energy tensor. For the de Sitter case, we briefly discuss the apparent dependency of the stability results on the choice of charts.

Index Saddle for the D1-D5-P Black String

• Amitabh Virmani

We construct a four-charge index saddle in the four-dimensional STU model as the BPS limit of the non-extremal four-charge black hole and show that it exhibits a new form of attractor behavior. We then uplift this solution successively to five and six dimensions, using the 4D-5D connection together with a chain of string dualities, to obtain the gravitational index saddle for the D1-D5-P black string. Finally, we take a systematic decoupling limit of this index saddle and recover the BTZ $\times S^3$ geometry that computes the supersymmetric index of the D1-D5 CFT.

Carrollian Holography and Black Hole Entropy in Three-Dimensional Gravity

• Tabasum Rahnuma (Korea Institute of Advance Studies (KIAS), Seoul)

In this talk, I will explain our study of the systematic expansion of $AdS_3$ Chern-Simons gravity in powers of the cosmological constant, with a focus on black hole thermodynamics. The bulk expansion generates an infinite tower of three-dimensional gravity theories invariant under successive extensions of Poincare symmetry, and we derive consistent boundary conditions and conserved charges at each order. On the boundary, the corresponding post-Carrollian expansion of the dual field theory is governed by conformal extensions of Carroll symmetry, obtained from contracting the two-dimensional conformal algebra. The black hole entropy interpolates order by order between the Virasoro Cardy formula and its $BMS_3$ counterpart, with each correction carrying a precise microscopic interpretation in the boundary theory. The exact matching between bulk thermodynamics and boundary state counting at every order reveals that the transition from $AdS/CFT$ to flat space holography has a controlled perturbative structure, and that Carrollian symmetry and its extensions emerge as the natural organizing principle.

Finite-N holography and the Giant Graviton Expansion

• Martí Rosselló (Academia Sinica, Taiwan)

The giant graviton expansion reorganizes finite-N indices in superconformal field theories as the large-N answer corrected by a systematic series of finite-N contributions. These corrections admit a natural holographic interpretation in terms of branes in the bulk, known as giant gravitons. I will discuss the derivation of this expansion for the half-BPS index of N=4 SYM directly from AdS5 × S5, and explain how the analytic continuation appearing in previous formulations is naturally understood as wall-crossing.

The hole, the ring, the string, and all that

• Dario Martelli (Università di Torino and INFN Torino)

In this talk, I will discuss supersymmetric solutions of five-dimensional gauged supergravity that are relevant to holography. I will present complementary approaches to studying the physics of these solutions, with particular emphasis on results obtained using equivariant localization. Various examples will be discussed, including a new solution and its associated thermodynamics, based on unpublished work.

Green’s function construction for late-time tail via Pseudo-spectral method

• Miok Park (Institute for Basic Science (IBS))

To improve the analytical description of gravitational-wave ringdown, this work investigates black hole spectroscopy using the pseudo-spectral method, which computes black hole frequency spectra through eigenvalue problems. Although quasinormal modes (QNMs) are well understood, the physical interpretation of the remaining spectral components remains unclear. We focus on purely imaginary eigenvalues in the low-frequency regime and analyze the perturbed Klein–Gordon equation using Green’s function methods, emphasizing branch-cut contributions that govern late-time tails. Unlike the conventional Wronskian approach, we construct the Green’s function directly from pseudo-spectral eigenvalues and eigenvectors through a Sturm–Liouville-like formulation. By comparing the two Green’s functions, we aim to establish a correspondence between the low-frequency imaginary eigenvalues and the late-time tail solutions.

Type IIB Supergravity Action and Holography

• Junho Hong (Sogang University)

In the prototypical AdS5/CFT4 correspondence, the free energy of N=4 SU(N) super Yang–Mills is commonly reproduced from the Euclidean on-shell action of five-dimensional gauged supergravity. A longstanding obstacle is that the conventional Type IIB pseudo-action evaluated on AdS5×S5 vanishes identically, apparently precluding a first-principles holographic comparison. A recent proposal by Kurlyand and Tseytlin, based on the Pasti–Sorokin–Tonin formulation, resolves this for a special class of backgrounds including the AdS5×S5 vacuum by introducing a topological term required for consistency, yielding a non-vanishing on-shell value in agreement with holography. In this talk, I will explain how this refinement can be extended to a broader class of Type IIB backgrounds via a generalized topological correction under milder conditions, encompassing AdS geometries of generic dimension and non-vanishing 2-form potentials. Tests of the proposal on non-trivial solutions—the Lunin–Maldacena background and the AdS4 S-fold— will also be provided. Our results place direct holographic comparisons within the ten-dimensional Type IIB framework on firmer ground.

Large-N saddle of a chiral Chern-Simons-matter theory

• Edoardo Colombo

Computing the large-$N$ limit of the $S^3$ free energy or the $S^2\times S^1$ supersymmetric indices of *chiral* $\mathcal N=2$ Chern-Simons-matter theories is a long-standing open problem. Focusing on a particular chiral quiver theory, the one dual to M-theory on $\text{AdS}_4\times Q^{1,1,1}/\mathbb Z_k\,$, we present the first analytic solution to the large-$N$ saddle point equations of a chiral quiver, successfully matching holographic predictions. The inspiration for the analytic ansatz comes from a numerical solution at $N\sim200$ that we have obtained using the method recently developed in 2510.24837. We discuss the relation between the large-$N$ saddle and the operator counting conjecture.

Radiation, holographic fluids, and the flat limit

• Gabriel Arenas-Henriquez

Gravitational radiation is well understood in asymptotically flat spacetimes, where it is encoded in the Bondi news, but its analogue in asymptotically AdS spacetimes is more subtle. In this talk, I will discuss a holographic perspective on this problem using a geometric formulation of fluid/gravity correspondence. For asymptotically locally AdS spacetimes, the radiative content can be characterized by boundary data, in particular the holographic stress tensor and the Cotton tensor. I will explain how this radiative structure can be reinterpreted in terms of out-of-equilibrium fluid dynamics in the dual boundary theory, with bulk radiation sourcing dissipative corrections and entropy production. I will then discuss the flat limit of this construction, in which the boundary fluid becomes Carrollian and the radiative data are related to Bondi news and to celestial observables such as energy detectors. Examples include accelerating black holes and Robinson-Trautman spaces.

TBA

• Jaydeep Kumar-Basak

Rotating End of the World

• Kyung Kiu Kim

We study the thermodynamics and interior structures of dynamical end of the world (EoW) branes in the rotating BTZ black hole. By mapping the induced metric of the branes to an effective Jackiw-Teitelboim (JT) system, we derive the first law of thermodynamics for the boundary conformal field theory (BCFT), incorporating boundary degrees of freedom. To construct this thermodynamics, we adopt two frameworks of black hole chemistry and the duality between the JT black hole and the Sachdev-Ye-Kitaev (SYK) model. In addition, we verify that the shadow entropy is equivalent to the boundary entropy via Hubeny-Ryu-Takayanagi (HRT) surfaces. Furthermore, we explore the possible interior configurations of the EoW brane inside the horizon. Two representative configurations, namely single and double-joint EoW branes, are considered. These disparate configurations share the same exterior brane configuration outside the horizon. By comparing their energies, we show that a transition could occur within the horizon.

Moduli-dependent one-loop entropy of hyperbolic BPS black hole in AdS4

• Imtak Jeon (Huzhou Normal University)

We study one-loop logarithmic corrections to the entropy of static hyperbolic BPS black holes in asymptotically AdS4 spacetime within N=2 Fayet–Iliopoulos gauged supergravity. In this setup, the classical BPS attractor mechanism exhibits flat directions, leaving scalar moduli on the horizon unfixed while the Bekenstein–Hawking entropy depends only on the charges. We show that quantum corrections induce a nontrivial dependence of the entropy on the horizon moduli, generating an effective quantum potential that dynamically stabilizes them. This provides an explicit realization of the quantum lifting of classical attractor flat directions. We will also comment on implications for the quantum structure of AdS black holes and possible connections to holography.

Resolving Black Hole Singularities in JT Theory

• Dongsu Bak (University of Seoul)

In JT gravity, naive Schwarzian quantum mechanics has a continuous spectrum, in contradiction with the finite black-hole entropy, which requires a discrete spectrum with level spacing of order e-S0. We show that restoring spectral discreteness and random-matrix statistics requires a left confining potential that becomes important when the renormalized wormhole length reaches order e+S0. This modification also resolves the black-hole singularity, alters late-time bulk dynamics, and leads to the disappearance of semiclassical horizons, with potentially observable consequences.

An Exact M2/M5 Duality from Giant Graviton Expansion

• Heng-Yu Chen

Deep Learning Bulk Spacetime from Boundary Quantum Data

• Keun-Young Kim

According to the holographic principle—one of the most influential frameworks in contemporary physics—gravitational physics in a bulk spacetime is dual to the quantum physics of a system defined on its boundary. We employ a deep learning approach to reconstruct the bulk spacetime geometry from boundary quantum data, such as conductivity and entanglement entropy. This method offers novel insights into the properties of quantum matter through their dual spacetime interpretation. Because our deep learning approach generalizes to a wide range of problems involving differential equations and integral formulations, it holds broad utility for diverse applications across physics and engineering.

Investigating the near-gap spectrum in the D1D5 CFT

• Shaun Hampton

In this talk I will discuss recent work investigating the non-BPS spectrum in the D1D5 CFT. In the free theory, non-BPS excitations are separated from BPS states by a spectral gap of order 1/N. These energies are lifted when one considers perturbations away from the free theory. We compute this lift and show, in the large N limit, that the second order corrections dominate over the first order contributions. Furthermore, we uncover an intriguing behavior where the lifting exhibits an integrable structure yielding a gap and near gap spectrum that is robust away from the free theory, features which may have important implications for black hole microstates in the D1D5 system.

One-loop Partition Functions from Quasinormal Modes and Trace Formulas

• Sang-Eon Bak (Arizona State University)

One-loop partition functions encode leading-order quantum corrections to the gravitational path integral and can be constructed from quasinormal modes and heat kernel methods. We investigate how exact computations of these quantities can be extended beyond highly symmetric backgrounds. Trace formulas provide a powerful framework connecting spectral data of differential operators to geometric data of the underlying manifold. In this talk, I will first review how the Selberg trace formula can be used to compute the one-loop partition function of massive scalar fields in the BTZ black hole background. I will then present how we develop a method to compute one-loop partition functions on broader classes of manifolds by using the Gutzwiller trace formula. We find that there are two geometric types whose properties lead to different spectral structures in the corresponding quasinormal modes and one-loop partition functions.

Quantum corrections to tidal Love number for Schwarzschild black holes

• Myungbo Shim (Yau Mathematical Sciences Center, Tsinghua University)

A sum rule for tidal Love number is derived from quantum field theory computations, which relates tidal susceptibility of a spinless body to transition rates of its single graviton emission processes. An analogous sum rule for electromagnetism is given as an example, which is substantiated by comparing it to the solved problem of the hydrogen atom. Based on the semiclassical Hawking radiation spectrum, a finite nonvanishing value for quantum corrections to the Love number of Schwarzschild black holes in general relativity is computed using the sum rule, which is known to classically vanish. If time permits, the role of tidal Love numbers in black hole thermodynamics would be discussed. This talk is based on [hep-th: 2011.03337] with Jung-Wook Kim.