Anti-de Sitter Fragmentation

TL;DR

This paper explores the stability and possible fragmentation of AdS_2 x S^2 near-horizon geometries of black holes, proposing that such configurations can break into disconnected universes, affecting black hole entropy calculations.

Contribution

It introduces the concept of AdS_2 fragmentation, analyzing zero-energy configurations and their implications for black hole entropy and stability in non-supersymmetric contexts.

Findings

Finite-energy excitations of AdS_2 x S^2 are suppressed.

Zero-energy configurations include branched and disconnected geometries.

AdS_D can be unstable against instanton-mediated fragmentation.

Abstract

Low-energy, near-horizon scaling limits of black holes which lead to string theory on AdS_2 x S^2 are described. Unlike the higher-dimensional cases, in the simplest approach all finite-energy excitations of AdS_2 x S^2 are suppressed. Surviving zero-energy configurations are described. These can include tree-like structures in which the AdS_2 x S^2 throat branches as the horizon is approached, as well as disconnected AdS_2 x S^2 universes. In principle, the black hole entropy counts the quantum ground states on the moduli space of such configurations. In a nonsupersymmetric context AdS_D for general D can be unstable against instanton-mediated fragmentation into disconnected universes. Several examples are given.