Possible astrophysical observables of quantum gravity effects near black holes

Abstract

Recent implications of results from quantum information theory applied to black holes have led to the confusing conclusions that require either abandoning the equivalence principle (e.g. the firewall picture), or locality, or even more unpalatable options. The recent discovery of a pulsar orbiting a black hole opens up new possibilities for tests of theories of gravity. We examine possible observational effects of semiclassical quantum gravity in the vicinity of black holes, as probed by pulsars and event horizon telescope imaging of flares. In some cases, pulsar radiation may be observable at wavelengths only two orders of magnitude shorter than the Hawking radiation, so precision interferometry of lensed pulsar images may shed light on the quantum gravitational processes and interaction of Hawking radiation with the space-time near the black hole. This paper discusses the impact on the pulsar radiation interference pattern, which is observable through the modulation index in the foreseeable future, and discusses a possible classical limit of non-locality.