Faculty of Mathematics, Physics
and Informatics
Comenius University Bratislava

Seminar of Department of Theoretical Physics - Martin Krššák (12.12.2023)

Tuesday 12.12.2023 at 14:00, Lecture rook F2/125

05. 12. 2023 00.37 hod.
By: Peter Maták

Martin Krššák:
Bulk gravitational action and teleparallel geometry

The action is a crucially important concept in physics, used to derive field equations and serving as the starting point for quantization. In general relativity, the original action introduced by Hilbert yields field equations but overlooks surface terms necessary for a consistent variational principle. In the 1970s, Gibbons and Hawking demonstrated that the Hilbert action needs to be supplemented with a surface term that plays a crucial role in path integral quantization and derivation of black hole entropy. I will briefly introduce these results, incorporating newer motivation from the holographic principle and the study of the black hole information paradox. Subsequently, I will demonstrate how this problem can be approached using the so-called bulk actions, also known as Einstein or Moller actions. While these actions do avoid some problems of Gibbons and Hawking, they are not covariant. I will then argue that these actions can be naturally cast into a covariant form using another of Einstein's inventions known as teleparallel geometry.