Speaker: Michał Piotrak (UCL, HU Berlin)

Title: Clock witnesses of black hole entropy

Abstract:
One of the main discrepancies between gravity and the quantum theory is the fact that the former is generally covariant and the latter is not. While it is possible to impose covariance laws on a quantum theory, as it has been done in the case of quantum field theory, it is not native to it and practical computations require symmetry breaking, e.g. to define time evolution. This can be to some extent resolved within the framework of relational quantum mechanics, in which there is no global time evolution, but rather passage of time is defined with respect to observers who carry clocks. Recently, it has been shown that, within this framework, gravitational entropy is observer-dependent. In this talk I will apply this concept to a specific case of two-dimensional gravity and show how it can be used to find novel a information-theoretical interpretation for black hole entropy.