Large N limit of Extremal Non-supersymmetric Black Holes

TL;DR

This paper investigates the large N limit of extremal non-supersymmetric Type-I black holes, revealing an asymptotic supersymmetry restoration that aligns D-brane and black-hole descriptions, and analyzing the near-horizon geometry via D-brane probes.

Contribution

It demonstrates that in the large N limit, supersymmetry effectively restores, unifying D-brane and black-hole pictures, and explores the near-horizon geometry using D-brane probes.

Findings

Agreement between D-brane and black-hole pictures due to supersymmetry restoration.

Effective low-energy action for D-brane probes matches in the large N limit.

Non-renormalization of mass and entropy persists at large N.

Abstract

The large N limit of extremal non-supersymmetric Type-I five-dimensional string black holes is studied from the point of view of D-branes. We find that the agreement between the D-brane and the black-hole picture is due to an asymptotic restoration of supersymmetry in the large $N$ limit in which both pictures are compared. In that limit Type-I string perturbation theory is effectively embedded into a Type-IIB perturbation theory with unbroken supersymmetric charges whose presence guarantees the non-renormalization of mass and entropy as the effective couplings are increased. In this vein, we also study the near-horizon geometry of the Type-I black hole using D5-brane probes to find that the low energy effective action for the probe is identical to the corresponding one in the auxiliary Type-IIB theory in the large N limit.