Open Strings in Exactly Solvable Model of Curved Spacetime and PP-Wave Limit

TL;DR

This paper explores superstring theory in a curved spacetime model, analyzing D-branes, supersymmetry enhancement, and the smoothing of spacetime singularities at high energy within an exactly solvable framework.

Contribution

It extends an exactly solvable string model to superstrings in curved spacetime, investigates D-branes, and reveals supersymmetry enhancement and singularity smoothing phenomena.

Findings

Spacetime singularities become smooth at high energy.

Existence of bulk D-branes due to electric flux.

Supersymmetry is enhanced in the Penrose limit.

Abstract

In this paper we study the superstring version of the exactly solvable string model constructed by Russo and Tseytlin. This model represents superstring theory in a curved spacetime and can be seen as a generalization of the Melvin background. We investigate D-branes in this model as probes of the background geometry by constructing the boundary states. We find that spacetime singularities in the model become smooth at high energy from the viewpoint of open string. We show that there always exist bulk (movable) D-branes by the effect of electric flux. The model also includes Nappi-Witten model as the Penrose limit and supersymmetry is enhanced in the limit. We examine this phenomenon in the open string spectrum. We also find the similar enhancement of supersymmetry can be occurred in several coset models.