Black Hole Entropy is Thermodynamic Entropy

TL;DR

This paper argues that black hole entropy should be understood as genuine thermodynamic entropy, presenting a simple model of a Black Hole Carnot cycle to support this claim, moving beyond information-theoretic interpretations.

Contribution

It introduces a straightforward thermodynamic model demonstrating that black hole entropy is fundamentally thermodynamic, not merely information-theoretic, challenging previous arguments.

Findings

Black hole entropy aligns with thermodynamic entropy through a Carnot cycle model.

Previous justifications relying on information theory are inadequate.

The model confirms black hole entropy as a genuine thermodynamic quantity.

Abstract

The comparison of geometrical properties of black holes with classical thermodynamic variables reveals surprising parallels between the laws of black hole mechanics and the laws of thermodynamics. Since Hawking's discovery that black holes when coupled to quantum matter fields emit radiation at a temperature proportional to their surface gravity, the idea that black holes are genuine thermodynamic objects with a well-defined thermodynamic entropy has become more and more popular. Surprisingly, arguments that justify this assumption are both sparse and rarely convincing. Most of them rely on an information-theoretic interpretation of entropy, which in itself is a highly debated topic in the philosophy of physics. We discuss some of the pertinent arguments that aim at establishing the identity of black hole surface area (times a constant) and thermodynamic entropy and show why these arguments are not satisfactory. We then present a simple model of a Black Hole Carnot cycle to establish that black hole entropy is genuine thermodynamic entropy which does not require an information-theoretic interpretation.