13ª Semana Integrada do Instituto de Física de São Carlos

On the nature of the black hole information problem

21 de ago. de 2023 14:00

1h 30m

Salão de Eventos USP

Prêmio YPM 14h00 - 15h30

Descrição

More than a century after its creation, general relativity is the most successful theory to describe gravitational phenomena at the classical level. Given its grandeur, it is even possible to study quantum effects in gravitation by considering quantum field theory in a curved spacetime background. However, although many developments have been made in the study of such effects, a satisfactory theory of quantum gravity is still an open question. One of the most intriguing aspects of these developments is the black hole information problem: a question about the final state of a black hole in light of its evaporation process, as predicted by the emission of particles with perfect thermal character. (1) In other words, one would like to understand if the information is really lost in the process of black hole evaporation, or how this inadequate conclusion can be used to construct an adequate theory of gravitation. (2) The goal of this work is to present the information problem and to consider, from a critical perspective, which concepts of general relativity, quantum field theory, and thermodynamics are minimally necessary for its formulation. First, we have reviewed the elements of general relativity necessary for the study of black holes and the information problem. Second, within this framework, we analyzed the classical aspects of black holes and the concepts of their formation in physically reliable spacetimes. Such an analysis was made by representing a black hole as a region with no escape, whose internal evolution does not affect the rest of spacetime, i.e., the outer region is causally and deterministically “well behaved”. To make such a description precise, we used the fact that, at sufficiently late times, the black hole is uniquely described by three parameters, its mass, angular momentum, and electric charge, which give rise to the uniqueness of the Kerr-Newman metric. (3) Third, following this description, we have used the symmetries of the spacetime, described the black hole boundary as a null geodesic congruence and considerations of the cosmic censor conjecture to derive several properties that are rigorous results of differential geometry. Currently, we are deriving relevant quantum effects using the formalism of quantum field theory in curved spacetime. At the same time, we are discussing how the assumptions used to derive the classical properties have to be interpreted in the light of quantum effects. This will finally enable us to discuss the relationship between the properties of black holes and thermodynamics, and thus to present the information problem.

Referências

1 WALD, R. M. The thermodynamics of black holes. Living Reviews in Relativity, v. 4, n. 1, p. 6-1-6-44, Dec. 2001.

2 UNRUH, W. G.; WALD, R. M. Information loss. Reports on Progress in Physics, v. 80, n. 9, p. 092002, July 2017.

3 HEUSLER, M. Black hole uniqueness theorems. Cambridge: Cambridge University Press, 1996. 249 p.