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.

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.

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.