Next Event

June 19th 2024, @IEM-CSIC

Conference Hall of CFMAC - CSIC. C/Serrano 121. Madrid

11:30h

Speaker: Thomas Thiemann (Friedrich-Alexander-Universität, Germany)

Title: Symmetry reduction, gauge reduction, backreaction and consistent higher order perturbation theory

Abstract: The gauge invariant description of perturbations of solutions of Einstein's equations with a given Killing symmetry plays an important role in classical and quantum General Relativity (GR). While at linear order and for fixed background the notion of perturbative gauge invariance is under good control, there appears to be no agreed upon generalisation to higher orders. This problem becomes even more difficult when allowing backreaction, i.e. interaction between the symmetric background and non- symmetric perturbations. There has been an important advance over the past decade in application to cosmology with backreaction at linear order which motivates the so- called hybrid approach to quantum cosmology. In this presentation we propose a quite different route to this problem which allows to reconcile all four notions for a general Killing symmetry and to any order. At linear order and for homogeneous backgrounds, this route and the hybrid approach are equivalent. An obvious application is quantum black hole evaporation.

15:30h

Speaker:  Beatriz Elizaga de Navascués (Louisiana State University, USA). 

Title: Entangled pairs in evaporating black holes

Abstract: In this talk we present a QFT study about the entanglement structure of the Hawking effect in evaporating scenarios. For this purpose, first we review the known concept of Hawking partners, as being the field modes that are entangled with, and thus purify, the thermal radiation. Then, we show how the definition of these partners can be generalized to any case where the temperature of the radiation increases over time according to the semiclassical evaporation process. Our explicit computation allows us to study the relative location of radiation and partner modes at past null infinity. Finally, we discuss some physical consequences of our results on the fate of quantum information in gravitational collapse.