Stringy Structure at the BPS Bound

TL;DR

This paper investigates the stringy structure of 1/2-BPS bound states of NS fivebranes with momentum or fundamental string charge, using exact worldsheet models to connect geometrical and Landau-Ginsburg descriptions, revealing singular limits linked to black hole formation.

Contribution

It develops an exact worldsheet description of BPS bound states using null-gauged sigma models and maps it to a Landau-Ginsburg model, elucidating singular limits and black hole formation mechanisms.

Findings

Derived the closed-form solution for NS5-F1 supertube

Mapped geometrical configurations to LG models via CY/LG correspondence

Identified singular limits corresponding to black hole formation

Abstract

We explore the stringy structure of 1/2-BPS bound states of NS fivebranes carrying momentum or fundamental string charge, in the decoupling limits leading to little string theory and to AdS3/CFT2 duality. We develop an exact worldsheet description of these states using null-gauged sigma models, and illustrate the construction by deriving the closed-form solution sourced by an elliptical NS5-F1 supertube. The Calabi-Yau/Landau-Ginsburg correspondence maps this geometrical worldsheet description to a non-compact LG model whose superpotential is determined by the fivebrane source configuration. Singular limits of the 1/2-BPS configuration space result when the fivebrane worldvolume self-intersects, as can be seen from both sides of the CY/LG duality - on the Landau-Ginsburg side from the degeneration of the superpotential(s), and on the geometrical side from an analysis of D-brane probes. These singular limits are a portal to black hole formation via the condensation of the branes that are becoming massless, and thus exhibit in the gravitational bulk description the central actors in the non-gravitational dual theory underlying black hole thermodynamics.