Entropy of Extremal Black Hole Solutions of String Theory

TL;DR

This paper investigates the thermodynamic entropy of extremal black holes in string theory, deriving a general form consistent with string state densities, and compares it with entanglement entropy, highlighting discrepancies.

Contribution

It derives a general thermodynamic entropy formula for extremal black holes in string theory and compares it with entanglement entropy, revealing differences.

Findings

Thermodynamic entropy differs from entanglement entropy for extremal black holes.

The derived entropy formula aligns with string state density calculations.

Entanglement entropy generally does not match thermodynamic entropy in these cases.

Abstract

For extremal black holes, the thermodynamic entropy is not proportional to the area. The general form allowed by thermodynamics is worked out for three classes of extremal black hole solutions of string theory and shown to be consistent with the entropy calculated from the density of elementary string states. On the other hand, the entanglement entropy does not in general agree with these results.