Low Tension Strings on a Cosmological Singularity

TL;DR

This paper investigates string scattering amplitudes on the Milne orbifold in the low tension limit, finding that ultraviolet divergences disappear and remaining divergences have sensible infrared interpretations, shedding light on singularity resolution.

Contribution

It systematically analyzes divergences in string scattering amplitudes on the Milne orbifold and connects low tension limits to higher spin theories and infrared behavior.

Findings

Ultraviolet divergences vanish in the low tension limit.

Remaining divergences have infrared interpretations.

Provides insight into singularity resolution in string theory.

Abstract

It has recently been argued that the singularity of the Milne orbifold can be resolved in higher spin theories. In string theory scattering amplitudes, however, the Milne singularity gives rise to ultraviolet divergences that signal uncontrolled backreaction. Since string theory in the low tension limit is expected to be a higher spin theory (although precise proposals only exist in special cases), we investigate what happens to these scattering amplitudes in the low tension limit. We point out that the known problematic ultraviolet divergences disappear in this limit. In addition we systematically identify all divergences of the simplest 2-to-2 string scattering amplitude on the Milne orbifold, and argue that the divergences that survive in the low tension limit have sensible infrared interpretations.