We are pleased to announce an upcoming seminar featuring Marco Bianchi from Universidad San Sebastián. Marco has an impressive academic background, having completed postdoctoral research at institutions such as Humboldt […]

We are happy to announce a new seminar by Laura Andrianopoli from Politecnico di Torino. Her research interests are mainly focused on Theoretical particle physics, more specifically supergravity, supersymmetry and […]

On the dynamics of isolated black holes

Abstract: There are two important physical processes around black holes that can be well described using relativistic perturbation theory: Scattering of electromagnetic and gravitational waves (and other fields) and quasinormal mode oscillations that take place, for instance, after the coalescence of a black hole binary. It is well-known that these physical processes, at first perturbative order, can be described in terms of gauge-invariant master functions. We have analyzed the space of all possible master functions for the case of non-rotating (Schwarzschild) black holes and we find two differentiated branches of solutions. One branch includes the known results: In the odd-parity case, the most general master function is an arbitrary linear combination of the Regge-Wheeler and the Cunningham-Price-Moncrief master functions whereas in the even-parity case it is an arbitrary linear combination of the Zerilli master function and another master function that is new to our knowledge. The other branch is very different since it includes an infinite collection of potentials which in turn lead to an independent collection master of functions which depend on the potential. We also find that of all them are connected via Darboux transformations. These transformations preserve physical quantities like the quasinormal mode frequencies and the infinite hierarchy of Korteweg-de Vries conserved quantities, revealing a new hidden symmetry in the description of the perturbations of Schwarzschild black holes: Darboux covariance. In this talk I will describe this hidden symmetry and how to apply it to the computation of scattering probabilities.

Modular invariance and thermal effective field theory

Abstract: I will review some old perspectives and results on modular invariance in higher-dimensional conformal field theories (D > 2). I will then discuss how thermal effective field theory provides a new perspective on the problem, letting us relate the leading subextensive piece of the thermal entropy on a sphere to a Casimir energy.

¿De verdad vivimos en un holograma?
XXV Aniversario de la correspondencia AdS/CFT

Hace 25 años, en noviembre de 1997, apareció en arXiv.org un manuscrito del físico argentino Juan Maldacena (U. Princeton), que introduciría un cambio ex- traordinario en la Física Teórica de Altas Energías. En el artículo se conjetura que las teorías de campos conformes (CFT) pueden ser vistas como un “holograma” de una teoría de gravedad (cuerdas) en el espacio anti-de Sitter (AdS), lo que se conoce como la correspondencia AdS/CFT. Hoy, 25 años más tarde, con más de 18.000 citas, el artículo de Maldacena se ha convertido en uno de los trabajos más citados de la historia. En esta charla abordaremos, en palabras simples, la idea y razones del porqué esta famosa correspondencia todavía tiene una influencia determinante en la física contemporánea.

Holographic Baryonic Matter without Flavor Branes

Abstract: In holographic models flavor is usually realized by introducing additional branes in a dual supergravity background. With this realization one is forced to work in a probe approximation or solve supergravity equations with sources, which typically requires introducing additional phenomenological simplifications. In addition, since there are no fields carrying baryon charge on the branes, baryonic matter is dual to solitonic configurations on the flavor branes, which makes challenging to describe a state with non-zero baryon density. Here we will show how these issues can be avoided by considering a holographic model where baryon symmetry is already realized in the dual supergravity sector. We construct confining solutions with non-zero baryon density that do not involve solitonic configurations despite the absence of dual fields carrying baryon charge. The model is a three-dimensional field theory cousin of Klebanov-Strassler and shares with it some interesting features like a duality cascade.

Axial Anomaly in Nonlinear Conformal Electrodynamics

Abstract: In this talk, we present the axial anomaly of Dirac spinors on gravitational instanton backgrounds in the context of nonlinear electrodynamics. In order to do so, we consider Einstein gravity minimally coupled to a recently proposed conformal electrodynamics that enjoys duality transformation invariance. These symmetries allow us to generalize the Eguchi-Hanson configuration while preserving its geometry. We then compute the Dirac index of the nonlinearly charged Eguchi-Hanson and Taub-NUT configurations. We find that there is an excess of positive chiral Dirac fermions over the negative ones which triggers the anomaly.

The Asymptotic Structure of Flat Spacetimes

Abstract: One of the most impressive achievements of theoretical physics is the “principle of least action” of classical mechanics, where a substantial number of phenomena can be described by just a single statement: the action must be stationary under arbitrary variations of the dynamical variables, with initial and final condition that must be held fixed. Therefore, the powerful formulation of classical and quantum mechanics based in the action, needs to be supplemented with a proper treatment of boundary conditions at infinity. This issue is of vital importance in the case of theories where the sufficiently rapidly decay of the fields at infinity is not a valid assumption. For example, the asymptotic symmetry analysis of General Relativity leads to the renowned BMS (Bondi-van der Burg-Metzner-Sachs) group, which corresponds to a fundamental piece in the understanding of the infrared dynamics of gravitational interactions. In this talk, the asymptotic structure of flat spacetimes will be discussed, focusing on the case of gravity and its interactions, starting in three spacetime dimensions and then discussing the higher dimensional case.

A New Weyl Invariant Theory of Gravity

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Carroll, Cotton and Ehlers

Abstract: Carroll geometries emerge as conformal boundaries of asymptotically flat spacetimes and have come to the forefront with the advent of flat holography. I will introduce these tools and show how they are used for unravelling the boundary manifestation of Ehlers' hidden Möbius symmetry present in four-dimensional Ricci-flat spacetimes that enjoy a time-like isometry. This is achieved in a designated gauge, where the three-dimensional Carrollian nature of the null conformal boundary is manifest and covariantly implemented. The action of the Möbius group is local on the space of Carrollian boundary data. Among these data, the Carrollian Cotton tensor plays a prominent role both in the Möbius electric/magnetic duality and for the determination of charges.

Explorando El Universo con Ondas Gravitacionales

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Covariant prescriptions for Holographic Entanglement Entropy

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Boundary and Plane Defect Criticality in the 3d O(N) Model

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Stampedes: Exactly Solvable Corners of QFT's

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Near AdS₂ Spectroscopy

Abstract: In this talk, I will describe holographic properties of near AdS₂ spacetimes that arise within spherically symmetric configurations of N=2 4-D supergravity, for both gauged and ungauged theories. These theories pose a rich space of AdS₂ x S² backgrounds, and their responses in the near-AdS₂ region are not universal. I will show that the spectrum of operator dual to the matter fields, and their cubic interactions, are sensitive to the properties of the background and the theory it is embedded in. The properties that have the most striking effect are whether the background is BPS or non-BPS, and if the theory is gauged or ungauged. The resulting differences will have an imprint on the quantum nature of the microstates of near-extremal black holes, reflecting that not all extremal black holes respond equally when kicked away from extremality.