BPS D-branes from an unstable D-brane in a curved background

Abstract

We find exact tachyon kink solutions of Dirac-Born-Infeld-type effective action describing an unstable D5-brane with a world volume 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 R1,4×T2×S3. 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 R1,2×T2 where T2 is inside S3. In one class of solutions we find an infinite degeneracy with respect to a constant magnetic field along the direction of the Neveu-Schwarz-Neveu-Schwarz field on S3. © 2005 The American Physical Society.