Quantum Aspects of Black Holes: From Microstates to Echoes and Somewhere In-Between

Abstract

In this thesis we explore quantum aspects of black holes from a variety of perspectives. In part I of this thesis we are motivated by the black hole information paradox to explore the idea of gravitational wave echoes from the perspective of black hole microstate statistics. We adopt the idea that a UV complete description of a black hole should involve exp(S) microstates in a thermal ensemble, where S = A/4G , is the Bekenstein Hawking entropy of the black hole. Furthermore, we take the stance that issues about the existence of echoes and black hole microstructure might be understood in terms of thermal correlators in the ensemble of microstates. We make use of the spectral form factor as a proxy for a thermal 2-point correlator calculation. We study how spacing statistics between microstates affects the thermalization behaviour of the black hole at late and early times. We find “echoes” in cases where there is substantial eigenvalue repulsion between individual microstates or if there are regularly spaced clusters of microstates. In part II of the thesis we analyze the process of information recovery and unitarity in black hole/gravity systems coupled to non-gravitational baths. In the first work of part II we study how the evaporation rate of a black hole changes when radiation is extracted near the horizon and apply our results to study how long it takes to recover information thrown into a black hole after the Page time. In the last work of part II we study entanglement wedge nesting in 3D AdS spacetimes cut off by an end-of-the-world brane. Finally, in part III we summarize the main results of the research works.