BLACK HOLE ENTROPY IN HIGHER CURVATURE GRAVITY

TL;DR

This paper explores black hole entropy in higher-curvature gravity theories, showing that entropy can be expressed as a geometric density and can satisfy the Second Law in certain cases, extending thermodynamics to complex gravitational actions.

Contribution

It demonstrates how black hole entropy can be formulated as a local geometric density in higher-curvature theories and discusses conditions under which the Second Law holds.

Findings

Black hole entropy can be expressed as a local geometric density.

In some higher-curvature theories, entropy satisfies the Second Law.

The paper analyzes polynomial Ricci scalar Lagrangians in this context.

Abstract

We discuss some recent results on black hole thermodynamics within the context of effective gravitational actions including higher-curvature interactions. Wald's derivation of the First Law demonstrates that black hole entropy can always be expressed as a local geometric density integrated over a space-like cross-section of the horizon. In certain cases, it can also be shown that these entropy expressions satisfy a Second Law. One such simple example is considered from the class of higher curvature theories where the Lagrangian consists of a polynomial in the Ricci scalar.