Holography, degenerate horizons and entropy

Abstract

We show that a realization of the correspondence AdS_2/CFT_1 for near extremal Reissner-Nordstrom black holes in arbitrary dimensional Einstein-Maxwell gravity exactly reproduces, via Cardy's formula, the deviation of the Bekenstein-Hawking entropy from extremality. We also show that this mechanism is valid for Schwarzschild-de Sitter black holes around the degenerate solution dS_2xS^n. These results reinforce the idea that the Bekenstein-Hawking entropy can be derived from symmetry principles.