Fractional S-branes on a Spacetime Orbifold

TL;DR

This paper explores the construction and properties of fractional S-branes in spacetime orbifolds, specifically focusing on the R^{1,d}/Z_2 model, and examines their role in brane decay and energy flux in string theory.

Contribution

It introduces fractional S-branes in spacetime orbifolds and analyzes their construction via open and closed string boundary states, advancing understanding of brane decay in time-dependent backgrounds.

Findings

Existence of fractional S-branes in spacetime orbifolds.

Construction methods for fractional S-branes using boundary states.

Application to brane nucleation and energy flux in string theory.

Abstract

Unstable D-branes are central objects in string theory, and exist also in time-dependent backgrounds. In this paper we take first steps to studying brane decay in spacetime orbifolds. As a concrete model we focus on the R^{1,d}/Z_2 orbifold. We point out that on a spacetime orbifold there exist two kinds of S-branes, fractional S-branes in addition to the usual ones. We investigate their construction in the open string and closed string boundary state approach. As an application of these constructions, we consider a scenario where an unstable brane nucleates at the origin of time of a spacetime, its initial energy then converting into energy flux in the form of closed strings. The dual open string description allows for a well-defined description of this process even if it originates at a singular origin of the spacetime.