Gong Show and Posters

Gong Shows

• Soumya Adhikari: Type IIB Supergravity Action and Holography

Abstract: 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 x 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 x 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 x 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 x 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.

• Paolo Arnaudo: Bouncing singularities in Schwarzschild: a geometric origin of the QNM convergence region

Abstract: In AdS/CFT, bouncing geodesics provide a sharp geometric diagnostic of black-hole singularities through the analytic structure of thermal correlators. In this talk I will explain that the same mechanism has a direct analogue in asymptotically flat Schwarzschild spacetime, arising in the null limit of radial spacelike geodesics which bounce off the black hole singularity. These complex-time “bouncing singularities” are not singularities of the physical Lorentzian spacetime, but they control the analytic structure of the retarded Green’s function for linear Schwarzschild perturbations. Building on a recent convergent mode decomposition of black hole perturbations, we show that the lightcone delimiting the convergence region of the late-time QNM expansion has a simple geometric origin in these bouncing singularities.

• Daniele Artico: Thermal CFTs in the Presence of Boundaries and Defects

Abstract: In this Gong talk, I map the kinematics and dynamics of thermal CFTs with boundaries and line defects. I derive general constraints on one-point functions for scalar, vector, and spin-2 operators, then present closed-form expressions for one- and two-point functions in free and interacting theories. Using direct calculations and dispersion relations, I show how thermal one-point functions are governed by elliptic theta functions, which automatically satisfy the KMS condition while encoding infinite winding sectors.

• João Vilas Boas: Multi-Particle Correlators with Higher KK Modes

Abstract: We consider heavy-heavy-light-light (HHLL) correlators in AdS/CFT, focusing in N=4 SYM.  We consider a particular heavy operator O_H given by a coherent superposition of multi-particle operators O_2^n, built out of the lightest chiral primary operator O_2. This state is dual to a BPS bubble geometry in the bulk. We study the quadratic fluctuations around this background to extract the HHLL correlators with two insertions of O_H and two “light” fields (in generic Kaluza-Klein mode) dual to the perturbation. In the "light" limit of the HHLL correlator, we compare the supergravity results to some correlators computed from the CFT. On the CFT side, these computations involve the double-particle bootstrap or the OPE of higher-point functions.

• Chen Bowen: New Kinematic Spaces from Holographic Entropy Cone

Abstract: One surprising lesson brought about by the AdS/CFT correspondence is that the bulk geometry reflects the entanglement structure of the boundary CFT state. Ryu-Takayanagi formula exemplifies this, connecting the area of an extremal surface with the entanglement entropy on the boundary. However, there are entanglement patterns beyond simple geometric objects, e.g. the holographic entropy cone program. In this work, we bridge the connection between those seemingly different perspectives, by defining a new kinematic space and studying its geometric and topological properties in two-sided black holes.

• Wen-Xin Lai: Replica Trick in a (simplified) String Theory, for TTbar Deformed CFTs

Abstract: The TTbar deformation is a special type of "solvable" deformation. When applied to CFTs, the deformed theory shows signs of nonlocality and can be further reformulated as a string theory. Under this framework, we develop worldsheet techniques to compute its entanglement entropy via a generalization of the replica trick in string theory. The result hints at a process where nonlocality is gradually introduced through the deformation and finally smooths out the UV cutoff of the original CFT. The talk will be based on arxiv:2507.15220.

• Francesco Mangialardi: Controlling 3D CFT Data using Thermal Correlators

Abstract: I will describe how correlation functions of a conformal field theory placed on the thermal geometry S^1 x S^2 can be used to obtain precise information about flat space CFT data, namely the spectrum and the OPE coefficients of primary operators. The focus will be primarily on thermal one-point functions. I will present the latest developments and applications in this line of research.

• Pedro Marto: O(d, d) Symmetric Backgrounds and Finite Coupling Holography

Abstract: Motivated by the possibility of probing the singularity structure of black holes solutions dual to field theories at finite coupling, we construct asymptotically AdS black brane solutions in a theory of gravity with an infinite series of curvature corrections. The action is based on an O(d, d) symmetric ansatz which has been argued to describe the classical NSNS sector of string theories. We find that, for this general class of theories, the singularity behind the horizon is not resolved by the curvature corrections. The approach to the singularity is however generically modified, being characterized by different Kasner exponents. We also show that, in the presence of a non-trivial dilaton, these types of curvature corrections can generate dynamically a negative cosmological in the region of small coupling. This provides a mechanism by which asymptotic freedom could emerge in the hypothetical string dual of QCD.

• Sarina Michael: Deformations of the Chiral SYK Chain and a Holographic BKT Phase Transition

Abstract: It was found recently (Altland et al. arXiv:2502.19370) that there is a holographic correspondence between chiral SYK chains and rotating BTZ black holes, connecting Majorana edge dynamics which appear in certain topological materials to their gravitational dual in one dimension higher. In the infrared, both sides are governed by the Alekseev–Shatashvili (AS) action, a generalization of the Schwarzian theory. We consider a deformation of this description by relevant bilocal operators and analyse it following the Wilsonian RG scheme which leads to a phase diagram with a critical line separating an SYK-stable phase from a deformation dominated one, reminiscient of a BKT transition. A microscopic origin of this deformation is provided by interactions between counterpropagating Majoranas. On the gravity side, they can be interpreted in terms of  matter fields propagating on a BTZ background. The transition itself corresponds to an instability towards condensation or chiral symmetry breaking depending on the dual channel.

• Ilias Papadimitriou: Thermalization of (1+1)d QFTs

Abstract: Thermalization remains an important open problem in quantum field theory. Two-dimensional quantum field theories provide a more tractable setting in which to study this question and may offer insights into thermalization in higher dimensions. In this context, the emergence of hydrodynamics is closely tied to the breakdown of conformal symmetry. However, this transition cannot be captured within standard conformal perturbation theory without resummation.

In this talk, I will briefly review recent developments and then focus on ongoing work aimed at understanding this problem through the lens of holography.

• Klaas Parmentier: 3d CFTs on Squashed Spheres

Abstract: We consider 2 limits in which the study of CFTs on curved 3-manifolds simplifies. In the limit of small deformations around the round 3-sphere, we can use conformal perturbation theory to show that the round 3-sphere extremizes the free energy. In the large deformation limit of circle bundles, where the circle becomes small, we can use thermal EFT to relate the free energy of different backgrounds, as we illustrate with free and holographic CFTs.

• Alexandros Stratoudakis: Deep Finite Temperature Bootstrap (Part II)

Abstract: We introduce a novel method to bootstrap crossing equations in Conformal Field Theory and apply it to finite temperature CFTs. The proposed approach does not rely on positivity constraints and does not employ uncontrolled truncation schemes. Instead, we capture the contribution of an infinite number of operators in conformal block expansions using suitable functions, which are bootstrapped (numerically) together with a finite number of exposed CFT data. Our approach at finite temperature employs three key ingredients: (i) the Kubo-Martin-Schwinger condition, (ii) thermal dispersion relations and (iii) Neural Networks that model spin-dependent tail functions within the conformal block expansions. We test the efficiency of the new method in the case of Generalized Free Fields and use it to perform a preliminary bootstrap analysis of double-twist thermal data in holographic CFTs.

This talk will be a joint presentation (3+3 minutes) with one of the paper's coauthors, Mitchell Wolley.

• Julio Virrueta: Non-Gaussian Fluid Effective Actions from Holography

Abstract: Recently, effective actions for fluctuating hydrodynamics have been constructed using holographic techniques up to second order in the amplitude expansion. In this talk I will explain how these methods can be extended to construct effective actions for fluids beyond the Gaussian approximation, allowing for interactions between hydrodynamic modes.

• Mitchell Woolley: Deep Finite Temperature Bootstrap (Part I)

Abstract: We introduce a new strategy to bootstrap crossing equations in CFT and apply it to CFTs at finite temperature. Our method does not rely on positivity and avoids uncontrolled truncation schemes. Instead, we capture the contribution of an infinite number of operators in conformal block expansions using suitable functions, which are numerically bootstrapped together with a finite number of exposed CFT data. Our approach at finite temperature employs three key ingredients: (i) the KMS condition, (ii) thermal dispersion relations and (iii) Neural Networks that model spin-dependent tail functions within the conformal block expansions. We test the efficiency of the new method in the case of Generalized Free Fields and use it to perform a preliminary bootstrap analysis of double twist thermal data in holographic CFTs.

This talk will be a joint presentation (3+3 minutes) with one of the paper's coauthors, Alexandros Stratoudakis..

Posters

• Sidan A: Diamonds in the Bulk and Large-N Scaling in AdS/CFT

• Soumya Adhikari: Type IIB Supergravity Action and Holography

• Chen Bowen: New Kinematic Spaces from Holographic Entropy Cone

• Chantelle Esper: Bulkcone Singularities and Complex Geodesics

• Wen-Xin Lai: Replica Trick in a (simplified) String Theory, for TTbar Deformed CFTs

• Pedro Marto: O(d, d) Symmetric Backgrounds and Finite Coupling Holography

• Joaquin Masias: Backreaction of Light Species in Minimal Black Hole Limits

• Sarina Michael: Deformations of the Chiral SYK Chain and a Holographic BKT Phase Transition

• Klaas Parmentier: 3d CFTs on Squashed Spheres

• Alexandros Stratoudakis: Deep Finite Temperature Bootstrap