The Rolling Tachyon Boundary Conformal Field Theory on an Orbifold

TL;DR

This paper analyzes a boundary conformal field theory with marginal deformation related to rolling tachyons and S-branes, using orbifold techniques and fermionization to perform open string computations at one loop.

Contribution

It extends fermionization methods to Z_2 reflection orbifolds and develops a framework for open string calculations at arbitrary rational radii.

Findings

Formulated the Z_2 reflection orbifold in boundary CFT.

Extended fermionization techniques for orbifold analysis.

Provided methods for open string computations at arbitrary rational radii.

Abstract

We consider the non-trivial boundary conformal field theory with exactly marginal boundary deformation. In recent years this deformation has been studied in the context of rolling tachyons and S-branes in string theory. Here we study the problem directly from an open string point of view, at one loop. We formulate the theory of the Z_2 reflection orbifold. To do so, we extend fermionization techniques originally introduced by Polchinski and Thorlacius. We also explain how to perform the open string computations at arbitrary (rational) radius, by consistently constructing the corresponding shift orbifold, and show in what sense these are related to known boundary states. In a companion paper, we use these results in a cosmological context involving decaying branes.