Entropy of Thermal CFTs on Curved Backgrounds

TL;DR

This paper uses holography to analyze the entropy of thermal conformal field theories on curved backgrounds with horizons, revealing universal relations between entanglement and gravitational entropy.

Contribution

It provides explicit calculations of entanglement entropy for CFTs on curved backgrounds with horizons using holography, including the relation to gravitational entropy and horizon degrees of freedom.

Findings

Entropy proportional to horizon area with CFT degrees of freedom

Dual description of CFT at different temperatures from horizons

Universality demonstrated for general (2+1)-dimensional AdS black holes

Abstract

We use holography in order to study the entropy of thermal CFTs on (1+1)-dimensional curved backgrounds that contain horizons. Starting from the metric of the BTZ black hole, we perform explicit coordinate transformations that set the boundary metric in de Sitter or black-hole form. For a de Sitter boundary, the dual picture describes a CFT at a temperature different from that of the cosmological horizon. We determine minimal surfaces that allow us to compute the entanglement entropy of a boundary region, as well as the temperature affecting the energy associated with a probe quark on the boundary. For an entangling surface that coincides with the horizon, we study the relation between entanglement and gravitational entropy through an appropriate definition of the effective Newton's constant. We find that the leading contribution to the entropy is proportional to the horizon area, with a coefficient that accounts for the degrees of freedom of a CFT thermalized above the horizon temperature. We demonstrate the universality of our findings by considering the most general metric in a (2+1)-dimensional AdS bulk containing a non-rotating black hole and a static boundary with horizons.