A note on the singularity theorem for supergravity SD-branes

TL;DR

This paper discusses a geometric no-go theorem for SD-brane spacetimes, explores cases that evade it, and considers implications for tachyon cosmology and potential future generalizations.

Contribution

It provides a geometric formulation of a singularity theorem for SD-branes and identifies physical scenarios that can escape this theorem.

Findings

Certain cosmological setups and half-SDp-branes evade the no-go theorem.

Space-filling SD8-branes may also escape due to Ramond-Ramond fields.

Tachyon cosmology remains viable despite the theorem.

Abstract

Recently, a singularity theorem for full SD-brane spacetimes was given in hep-th/0305055. We comment on the relation between this and previous work as well as provide a more geometric formulation interpreted as a no-go theorem. We then point out that some setups of physical interest escape the theorem: cosmological applications, half-SDp-branes and decaying unstable Dp-branes for general p. We also provide indications that the space-filling full SD8-brane (in d=10) escapes as well, because of the important role of Ramond-Ramond fields. In any case, tachyon cosmology is not ruled out by the no-go theorem. Lastly, we remark upon interesting directions for potential generalizations of the theorem, and quantum corrections.