Time Evolution of Temperature and Entropy of Various Collapsing Domain Walls

TL;DR

This paper studies how the temperature and entropy of collapsing domain walls evolve over time, considering different topologies and a cosmological constant, and compares the results to black hole thermodynamics.

Contribution

It extends previous work by analyzing the effects of topology and cosmological constant on the thermodynamics of collapsing domain walls using quantum and semi-classical methods.

Findings

Temperature approaches Hawking temperature at late times

Entropy tends to a constant close to Hawking entropy

De Sitter and BTZ walls show periods of decreasing entropy

Abstract

We investigate the time evolution of the temperature and entropy of gravitationally collapsing domain walls as seen by an asymptotic observer. In particular, we seek to understand how topology and the addition of a cosmological constant affect the gravitational collapse. Previous work has shown that the entropy of a spherically symmetric collapsing domain approaches a constant. In this paper, we reproduce these results, using both a fully quantum and a semi-classical approach, then we repeat the process for a de Sitter Schwarzschild domain wall (spherical with cosmological constant) and a (3+1) BTZ domain wall (cylindrical). We do this by coupling a scalar field to the background of the domain wall and analyzing the spectrum of radiation as a function of time. We find that the spectrum is quasi-thermal, with the degree of thermality increasing as the domain wall approaches the horizon. The thermal distribution allows for the determination of the temperature as a function of time, and we find that the late time temperature is very close to the Hawking temperature and that it also exhibits the proper scaling with the mass. From the temperature we find the entropy. Since the collapsing domain wall is what forms a black hole, we can compare the results to those of the standard entropy-area relation. We find that the entropy does in fact approach a constant that is close to the Hawking entropy. However, both the de Sitter Schwarzschild domain wall and the (3+1) BTZ domain wall show periods of decreasing entropy, which suggests that spontaneous collapse may be prevented.