Astrophysical Black Hole horizons in a cosmological context: Nature and possible consequences on Hawking Radiation

TL;DR

This paper investigates the nature of black hole horizons within a cosmological setting, revealing how cosmic background radiation influences horizon types and discussing implications for Hawking radiation.

Contribution

It introduces a semi-tetrad covariant approach to analyze horizon evolution in realistic cosmological scenarios, highlighting the bifurcation and nature of apparent horizons.

Findings

Inner horizon is timelike

Outer horizon becomes spacelike due to CBR influx

Implications for Hawking radiation in astrophysical contexts

Abstract

This paper considers the nature of apparent horizons for astrophysical black hole situated in a realistic cosmological context. Using semi-tetrad covariant methods we study the local evolutions of the boundaries of the trapped region in the spacetime. For a collapsing massive star immersed in a cosmology with Cosmic Background Radiation (CBR), we show that the initial 2 dimensional marginally trapped surface bifurcates into inner and outer horizons. The inner horizon is timelike while the continuous CBR influx into the black hole makes the outer horizon spacelike. We discuss the possible consequences of these features for Hawking radiation in realistic astrophysical contexts.