On the nature of black hole entropy

TL;DR

This paper argues that black hole entropy only accounts for states influencing the outside, challenges the holographic principle, and proposes a generalization of black hole thermodynamics to partial horizons.

Contribution

It introduces a novel perspective on black hole entropy, emphasizing influence on the outside, and extends thermodynamics concepts to partial horizons in general spacetimes.

Findings

Black hole entropy counts only external-influencing states.

Challenges to the holographic principle are discussed.

A generalization to partial horizons is proposed.

Abstract

I argue that black hole entropy counts only those states of a black hole that can influence the outside, and attempt (with only partial success) to defend this claim against various objections, all but one coming from string theory. Implications for the nature of the Bekenstein bound are discussed, and in particular the case for a holographic principle is challenged. Finally, a generalization of black hole thermodynamics to "partial event horizons" in general spacetimes without black holes is proposed.