Talks

TALKS

Tobias Canavesi

Title: “Scalar correlators and normal modes in holographic neutron stars”

Abstract: “We explore the normal modes of a scalar operator in the holographic neutron star background and its two point correlator, and investigate their relation with the thermodynamic instabilities of such background that were previously reported in https://iopscience.iop.org/article/10.1088/1361-6382/abb1f5”

Marina David

Title: “Holographic Approaches to AdS Black Hole Entropy”

Abstract: “Significant progress has been made regarding the microstate counting of extremal AdS black holes in the context of AdS/CFT, where the Cardy-like limit on the field side theory has often been used. I will discuss the implications of this limit on the gravity side and how it translates to a parameter space limit on the black hole solution. This limit, referred to as the gravitational Cardy limit, is applied to the Bardeen Horowitz near-horizon geometry to reproduce the Bekenstein-Hawking entropy via the Kerr/CFT correspondence, yielding a third approach to the computation of the entropy. Relaxing the gravitational Cardy limit, the computation can be further extended to near-extremality, where the heat capacity is found. For each case, extremal and near-extremal, the entropy from these different approaches match, providing a unique and universal expression for the entropy.”

Alfredo Gonzalez-Lezcano

Title: “Precision microstate counting of black hole entropy from N=1 toric quiver gauge theories”

Abstract: “We apply the AdS/CFT correspondence to investigate the entropy of five-dimensional, electrically charged rotating black holes. We do so by computing a field theoretical observable called the superconformal index. Specifically, we first study the superconfomal index of a large class of four-dimensional toric quiver gauge theories using a Bethe-Ansatz approach in the large N limit. We present explicit results for field theories arising from a stack of $N$ D3 branes at the tip of toric Calabi-Yau cones whose gravity dual are IIB string theories on AdS$_5 \times $ Sasaki-Einstein manifold. For a suitable choice of the chemical potentials of the theory we find agreement of the superconformal index and the function whose Legendre transform yields the black hole entropy.”

Anderson Seigo Misobuchi

Title: “Traversable wormholes from a sparse SYK model”

Abstract: “We consider a sparse SYK model whose Hamiltonian is defined on a regular hypergraph with kN independent terms. It has been shown that this model displays similar features of the original fully connected SYK model such as the quantum chaotic behavior for k of order unit. The sparsity property makes computational simulations much more tractable allowing the study of finite N effects. In this work, we study a system composed of two copies of the sparse SYK model coupled by a bilinear interaction. This model is inspired by the Maldacena and Qi model which has an eternal traversable wormhole as the gravitational picture. We study the transmission of signals between the two systems and we diagnose whether or not these signals can be interpreted as traversing a wormhole.”

Javier Moreno

Title: “Disks globally maximize the entanglement entropy in $2+1$ dimensions”

Abstract: “The entanglement entropy corresponding to a smooth region in general three-dimensional CFTs contains a constant universal term $-F$. For a disk region, this term coincides with the free energy on $\mathbb{S}^3$ and provides an RG-monotone for general theories. In this talk, we will argue that $F$ is globally minimized by disks with respect to arbitrary regions and for general theories. The proof makes use of the strong subadditivity of entanglement entropy and the geometric fact that one can always place an osculating circle within a given smooth entangling region. In addition, we provide accurate approximations to $F$ valid for general CFTs in the case of elliptic regions for arbitrary values of the eccentricity which we check against lattice calculations for free fields. We also evaluate $F$ numerically for more general shapes in the so-called "Extensive Mutual Information model'', verifying the general bound.”

Fábio Novaes

Title: “Generalized Gibbs Ensemble of 2D CFTs with U(1) charge from the AGT Correspondence”

Abstract: “The thermalization of isolated quantum systems can be explained by the Eigenstate Thermalization Hypothesis (ETH) using the standard Gibbs ensemble. However, in the presence of integrable charges, thermalization is better described by a Generalized Gibbs Ensemble. In this talk, we discuss the Generalized Gibbs Ensemble of 2D CFTs with a U(1) charge and an infinite set of conserved charges of an integrable hierarchy related to the AGT correspondence. We also discuss the holographic realization of these integrable charges in the AdS3/CFT2 correspondence, and connections with Lifshitz field theories and anisotropic Cardy formulas.”

David Pereñiguez

Title: “Quasinormal modes of NUT-charged black branes in AdS/CFT”

Abstract: “Quasinormal modes (QNM) of black holes in Anti-de Sitter space correspond, according to AdS/CFT, to poles of thermal correlators in the dual theory. Using the powerful results of 4d black hole perturbation theory — namely the Newman-Penrose formalism, Teukolsky’s equations and Hertz’s reconstruction map, I will derive master equations and holographic boundary conditions for gravitational perturbations. This leads, for the first time, to the QNM frequency spectrum of a NUT-charged space. The results provide definite holographic predictions regarding the hydrodynamic behaviour of the dual plasma. I will conclude by discussing stability against scalar and gravitational perturbations. “

Aaron Poole

Title: “Charges in asymptotically locally de Sitter spacetimes”

Abstract: “In this talk I will discuss conserved quantities in asymptotically locally de Sitter (dS) spacetimes. I will begin by motivating this work within the aim of developing a framework for gravitational waves in dS for full nonlinear general relativity. I will then review the asymptotics of de Sitter spacetimes, before showing that one can use the tools of the covariant phase space formalism, together with techniques from AdS/CFT, to derive expressions for conserved quantities. I will present flux formulae which capture the effects of outgoing gravitational radiation, illustrated via application to exact solutions of the field equations.”

Salomon Zacarias

Title: “On marginal deformations of a class of AdS3 N=(4,0) backgrounds”

Abstract: “I will discuss marginal deformations of warped AdS3 solutions preserving small N=(0,4) supersymmetry in massive IIA supergravity. The backgrounds are obtained by a sequence of duality transformations and define a whole family of new solutions. I will study some observables that characterise these new solutions like the quantised charges, associated Hannany-Witten brane set-ups, and the holographic central charge. The new solutions preserve N=(0,4) supersymmetry and support a dynamical SU(2) structure on the internal five-dimensional space. Field theory aspects o

GONG SHOW

Davide Bufalini

Black hole microstates from the worldsheet

We consider an exact worldsheet description of a string propagating in a specific family of black hole microstate geometries, whose description is given in terms of a (null-)gauged Wess-Zumino-Witten model. We will briefly discuss how the consistency of the worldsheet theory is in a one-to-one connection with smoothness, absence of horizons and closed timelike curves of the bulk theory. Finally, we will also mention how worldsheet correlators are related to correlators of the dual D1D5 CFT.

Anthonny Freddy Canazas Garay

Non-planar correction to Wilson loop correlators in N=4 SYM

After reviewing some relevant facts about holography and Wilson loops (WL's), we discuss the issue of handle corrections (at strong coupling) to the leading result. We consider two coincident circular WL's, but with opposite orientations in space time and internal space. It is enough to consider (to this order) the coupling of the string worldsheet to the metric, dilaton and Kalb-Ramond field. The necessary techniques for the calculation are described.

Rodrigo Castillo Vasquez

Entanglement entropy in cubic gravitational theories

I will present the derivation of the functional needed to compute the holographic entanglement entropy for a generic gravitational theory whose action contains terms up to cubic order in the Riemann tensor, and in any dimension. I will discuss some things about how the splitting problem arises in this context. I will also present the application of our results to the particular examples of a boundary disk and a boundary strip in a state dual to 4-dimensional Poincaré AdS in Einsteinian Cubic Gravity, where we obtained the bulk entanglement surface for both functionals and found that causal wedge inclusion is respected for the two splittings considered and a wide range of values of the cubic coupling.

Alfredo Grillo

Gravitational waves physics from quantum field theory

Recently a striking connection between the quantum Seiberg-Witten curves of $\mathcal{N} = 2$ SYM theories with Omega-background and the differential equations governing the linear perturbations of both black holes and horizonless geometries has been found. In tandem with the AGT correspondence, relating SYM theories to CFTs, this development provides a new approach to the computation of fundamental observable quantities of binary mergers, such as the spectrum of quasi-normal modes (QNMs) and the tidal Love numbers. Even though both the field theory and gravity sides admit a clear construction in terms of branes in some cases, the full scope of this gauge/gravity duality is yet to be understood. After introducing the framework for theories with $SU(2)$ gauge group we will show results on the computation of QNMs using the Nekrasov-Shatashvili construction of the SYM prepotential for Kerr-Newman BHs.

Joaquin Liniado

What is so central about the central charge?

We discuss the appearance of the Virasoro algebra as the symmetry algebra of two dimensional conformal field theories by introducing the idea of a mathematical obstruction. We argue why a central extension of the Witt algebra is required to obtain well defined unitary representations. This alternative perspective leads to the natural question of how can we relate this mathematical obstruction to the soft breaking of conformal symmetry due to the introduction of an external scale. In other words: What is so central about the central charge?

Lucas Emilio Martin

Winding Modes and the reflection symmetry in ads3

We have computed the contact term of the two-point function for the SL(2, R)-WZNW model in the winding sector. After reviewing some generalities of the model and its Euclidean counterpart, we will discuss the reflection symmetry for the spectral flowed sector. We will define the corresponding intertwining operator and use it to find the explicit form of the contact term of the propagator for a vertex carrying an arbitrary amount of spectral flow. Finally, we will enhance the already known integral expression of a singly flowed vertex in order to reproduce such contact term directly in the space-time picture.

Sergio Morales-Tejera

Chiral Magnetic Effect in the Quark-Gluon Plasma from Holography

The Chiral Magnetic Effect (CME) is the generation of an electric current in a chirally imbalanced medium in the presence of an external magnetic field. In particular, it is expected to manifest itself in the quark-gluon plasma (QGP) in heavy ion collisions, leading to charge separation. Such phenomenon is currently searched for in the data of the isobar run at RHIC. However, several experimental and theoretical uncertainties hardens the task of understanding the realization of the CME in the QGP. Here we construct a holographic model to study one of the uncertainties, namely the interplay between the build up time of the CME and the finite lifetime of the external magnetic field. After matching parameters to QCD we find that the CME build up time is short enough to be effective at RHIC energies but might be too short to be effective at LHC energies.

Marcelo Oyarzo

New topological Lifshitz black holes in Einstein-Yang-Mills-Dilaton with rich thermodynamics properties

We construct new black holes which may asymptote to a topological Lifshitz spacetime in the Einstein-Yang-Mills-Dilaton theory

for SU(2), and we provide as well a new interpretation of known solutions in this system. The black holes belong to three different families classified by the self-interacting potential of the scalar. The non-abelian sector is considered as the meron ansatz, which in spite of being non-spherically symmetric, leads to a spherically symmetric stress-tensor ensuring that we are in a non-abelian sector of the theory. One set of solutions has a cosmological horizon, where we find black holes with one and two horizons; we build its Penrose diagram as well. Also in this set, there is a solution whose horizons radii are given by W-Lambert functions. Particular properties of this special function allow us to prove that the first law of thermodynamics holds for both the black hole horizon and the cosmological horizon. The second set of solutions has a boundary at spatial infinity similar to AlAdS solutions. For this set, we find black holes with one, two and three black hole horizons, the latter may depict a black hole inside a black hole. In particular, the solutions with two horizons present three types of black holes, instead of two as in the Schwarzschild-AdS solution. We study the thermodynamics and phase transitions for both sets of solutions and we compute the energy content using the covariant phase space. Some comments regarding the embedding of these solutions in N=4 gauged SU(2)xSU(2) supergravity in four dimensions are also given.

Gabriel Palau

Haag duality for a free QFT

Haag duality is a remarkable property in QFT stating that the commutant of the algebra of observables localized in some region of spacetime is exactly the algebra associated to the causally disconnected region. It is a strong condition on the local structure and has direct consequences on entanglement measures. It was first shown to hold for a free scalar field and causal diamonds by Araki in 1964 and later by many authors in different ways. In particular, Eckmann and Osterwalder (EO) used Tomita-Takesaki modular theory to give a direct proof. However, it is not straightforward to relate this proof to the works of Araki, since they rely on three intertwined CCR representations (called Fock, Segal and Weyl representations). Also EO work as starting point assumes duality holds in the so called ``first quantization'' in the Weyl representation. It is our purpose to first introduce the works of Araki in a more easy-to-read but still rigorous and self-contained fashion, and show how Haag duality is stated in all three representations and in both first and second quantizations (and their immediate combination). This permits to understand the setting of the EO proof of Haag duality. There is nothing essentially new in this manuscript, with the exception of what we consider a simplification of EO proof that uses the adjoint of the Tomita operator instead of introducing several auxiliary operators. We hope this note will be useful for those seeking to understand where Haag duality comes from in a free QFT. arXiv:2108.01257

Martín Parlanti

Deep Inelastic Scattering of Glueballs and Baryons from String Theory

Deep Inelastic Scattering of charged leptons from glueballs is considered using the AdS/CFT duality. We study glueballs in the SU(Nc) N=4 supersymmetric Yang- Mills theory considering both large Nc and 1/Nc^2 corrections. We calculated hadronic tensor and derived structure functions.

Constanza Quijada

Phase transition for charged AdS soliton background

In this work we study the thermodynamics and the phase transitions between planar charged AdS black hole and charged AdS soliton. The charged AdS soliton is obtained as a double analytic continuation of the mentioned black hole metric. Our work shows that there are phase transitions between both solutions and that these depend on the electric potential, the magnetic flux and the temperature.