Black hole entropy: departures from area law

TL;DR

This paper examines how quantum corrections and specific black hole properties can cause deviations from the classical area law for black hole entropy, highlighting differences in extremal and non-extremal cases.

Contribution

It discusses potential departures from the semiclassical area law for black hole entropy, considering quantum effects and extremal black holes.

Findings

Quantum corrections can alter entropy calculations.

Extremal black holes show breakdown of area dependence.

Cutoff dependence varies between black hole types.

Abstract

The thermodynamic and euclidean functional integral approaches to black hole entropy are discussed. The existence of some freedom in the definition of the entropy is pointed out and the possibility of a departure from the semiclassical expression discussed in the light of quantum corrections. The semiclassical area dependence of the entropy of matter in the background of a black hole is also reviewed and shown to break down in the case of extremal black holes. The cutoff dependence is shown to be different for the extreme dilatonic and Reissner - Nordstrom black holes.