BPS D-branes from an Unstable D-brane in a Curved Background

TL;DR

This paper constructs exact tachyon kink solutions on an unstable D5-brane in a curved background, revealing their interpretation as composites of lower-dimensional D-branes and strings, with specific BPS configurations and degeneracies.

Contribution

It provides explicit solutions for tachyon kinks on unstable D-branes in a curved background, connecting them to lower-dimensional branes and fundamental strings with novel degeneracy features.

Findings

Solutions describe D4D2F1 composites wrapped on R^{1,2}×T^2

In the BPS limit, solutions become stable D-brane configurations

Existence of infinite degeneracy with magnetic field variations

Abstract

We find exact tachyon kink solutions of DBI type effective action describing an unstable D5-brane with worldvolume gauge field turned on in a curved background. The background of interest is the ten-dimensional lift of the Salam-Sezgin vacuum and, in the asymptotic limit, it approaches ${\rm R}^{1,4}\times {\rm T}^2\times {\rm S}^3$. The solutions are identified as composites of lower-dimensional D-branes and fundamental strings, and, in the BPS limit, they become a D4D2F1 composite wrapped on ${\rm R}^{1,2}\times {\rm T}^2$ where ${\rm T}^2$ is inside ${\rm S}^3$. In one class of solutions we find an infinite degeneracy with respect to a constant magnetic field along the direction of NS-NS field on ${\rm S}^3$.