Horizon spectroscopy in and beyond general relativity

Abstract: In this work we generalize the results for the entropy spectra typically derived for black holes in general relativity to a generic horizon within the spherically symmetric (asymptotically flat and non-flat) space-times of more general theories of gravity. We use all the standard --- Bekenstein's universal lower bound on the entropy transition, the highly damped quasi-normal modes and reduced phase-space quantization --- approaches to derive the spectra. In particular, the three approaches show that the Bekenstein-like spectra for the horizon entropy is a robust result. Our results confirm the suggestion made relatively recently by an independent fourth argument by Kothawala et al [1].