String Propagators in Time-Dependent and Time-Independent Homogeneous Plane Waves

TL;DR

This paper constructs and analyzes string propagators in specific homogeneous plane wave backgrounds, revealing how background fields influence string behavior near singularities and in smooth settings.

Contribution

It provides explicit constructions of closed string propagators in both time-dependent and time-independent homogeneous plane wave backgrounds, highlighting the background field effects.

Findings

String propagators near null singularities are explicitly constructed.

Background fields influence the structure of string propagators, expressed via hypergeometric functions.

Conformal invariance simplifies the propagator expressions in constant dilaton backgrounds.

Abstract

For a special time-dependent homogeneous plane wave background that includes a null singularity we construct the closed string propagators. We carry out the summation over the oscillator modes and extract the worldsheet spacetime structures of string propagators specially near the singularity. We construct the closed string propagators in a time-independent smooth homogeneous plane wave background characterized by the constant dilaton, the constant null NS-NS field strength and the constant magnetic field. By expressing them in terms of the hypergeometric function we reveal the background field dependences and the worldsheet spacetime structures of string propagators. The conformal invariance condition for the constant dilaton plays a role to simplify the expressions of string propagators.