On the instability of 3d null singularities

TL;DR

This paper investigates the instability of null singularities in 3D Lorentzian orbifolds, showing that even minimal matter causes the singularity to become spacelike, highlighting challenges in string propagation near such singularities.

Contribution

It provides a detailed analysis of null singularity instability in 3D Lorentzian orbifolds using classical gravitational backgrounds, extending previous studies on string propagation.

Findings

Null singularities become spacelike with any matter addition.

The singularity can be modeled as a limit of the BTZ black hole.

String propagation is affected by the singularity's nature.

Abstract

String propagation on a three-dimensional Lorentzian string orbifold with a null singularity has been studied by Horowitz and Steif, and more recently by Liu, Moore and Seiberg. We analyze the target space as a classical gravitational background. The singularity becomes spacelike when an arbitrarily small amount of matter is thrown at the singularity. This can be seen directly by studying the null singularity as a limit of the M=0, J=0 BTZ black hole metric.