Comments on Half S-Branes

TL;DR

This paper reformulates the boundary state of half S-branes in bosonic string theory using matrix models, providing new insights into annulus amplitudes and resummation of exponential couplings.

Contribution

It introduces a matrix model representation of the boundary state and annulus amplitude for half S-branes, offering a novel analytical framework.

Findings

Boundary state expressed as a grand canonical partition function of a unitary matrix model.

Annulus amplitude represented as a grand canonical partition function of a two-matrix model.

Resummation of exponentially growing couplings in the annulus amplitude.

Abstract

Following hep-th/0305177, we write the boundary state of half S-brane in bosonic string theory as a grand canonical partition function of a unitary matrix model. From this representation, it follows that the annulus amplitude can be written as a grand canonical partition function of a unitary two-matrix model. We also show that the contribution of the exponentially growing couplings to the timelike oscillators can be resummed in a certain annulus amplitude.