Spacelike Branes

TL;DR

This paper explores spacelike branes (S-branes) in string theory, showing they are time-dependent solutions with charge, related to tachyon fields on unstable D-branes, and constructs their boundary states and supergravity solutions.

Contribution

It demonstrates that S-branes arise as time-dependent solutions in string theory with charge, and constructs their boundary states and supergravity solutions.

Findings

S-branes carry RR charges defined via sphere integrals.

SD-branes carry the same RR charges as S-branes.

Supergravity solutions for S-branes are constructed in specific cases.

Abstract

Scalar field theories with appropriate potentials in Minkowski space can have time-dependent classical solutions containing topological defects which correspond to S-branes - i.e. branes all of whose tangential dimensions are spacelike. It is argued that such S-branes arise in string theory as time-dependent solutions of the worldvolume tachyon field of an unstable D-brane or D-brane-anti-D-brane pair. Using the known coupling of the spacetime RR fields to the worldvolume tachyon it is shown that these S-branes carry a charge, defined as the integral of a RR field strength over a sphere (containing a time as well as spatial dimensions) surrounding the S-brane. This same charge is carried by SD-branes, i.e. Dirichlet branes arising from open string worldsheet conformal field theories with a Dirichlet boundary condition on the timelike dimension. The corresponding SD-brane boundary state is constructed. Supergravity solutions carrying the same charges are also found for a few cases.