Horizon Entropy

TL;DR

This paper reviews how the laws of black hole thermodynamics and their statistical mechanics foundations extend to more general causal horizons like de Sitter and Rindler horizons, based on local entropy density.

Contribution

It argues for the generalization of black hole thermodynamics laws to causal horizons using the concept of local horizon entropy density.

Findings

Laws of thermodynamics extend to causal horizons.

Statistical mechanical interpretation applies to these horizons.

Local entropy density is key to this generalization.

Abstract

Although the laws of thermodynamics are well established for black hole horizons, much less has been said in the literature to support the extension of these laws to more general settings such as an asymptotic de Sitter horizon or a Rindler horizon (the event horizon of an asymptotic uniformly accelerated observer). In the present paper we review the results that have been previously established and argue that the laws of black hole thermodynamics, as well as their underlying statistical mechanical content, extend quite generally to what we call here "causal horizons". The root of this generalization is the local notion of horizon entropy density.