Free string evolution across plane wave singularities

TL;DR

This paper investigates how free strings behave near singular plane wave geometries, finding that finite excitation energy constraints prevent consistent propagation across such singularities in scale-invariant spacetimes.

Contribution

It provides a detailed analysis of string propagation in singular backgrounds and establishes conditions under which propagation is inconsistent.

Findings

Finite excitation energy excludes propagation across singularities.

Scale-invariance of spacetime prevents consistent string evolution.

Analysis covers both center-of-mass and excited string modes.

Abstract

In these proceedings, we summarize our studies of free string propagation in (near-)singular scale-invariant plane wave geometries. We analyze the singular limit of the evolution for the center-of-mass motion and all excited string modes. The requirement that the entire excitation energy of the string should be finite excludes consistent propagation across the singularity, in case no dimensionful scales are introduced at the singular locus (in an otherwise scale-invariant space-time).