Closed String Tachyons and Their Implications for Non-Supersymmetric Strings

TL;DR

This paper investigates the effective action of closed string tachyons in non-supersymmetric string theories, revealing a positive quartic term and analyzing their dynamical evolution, with implications for stability and control in string models.

Contribution

It provides a systematic computation of the effective action for light closed string tachyons and explores their classical dynamics in a controlled regime.

Findings

The quartic term for the tachyon is positive in a specific field basis.

Homogeneous configurations tend to evolve into regimes where calculations become unreliable.

The study offers insights into the stability of non-supersymmetric string backgrounds.

Abstract

Closed string tachyons have long been somewhat mysterious. We note that there is often a regime in the classical moduli space in which one can systematically compute the effective action for such fields. In this regime, the tachyon is light, and cannot be integrated out. Instead, one must consider the combined dynamics of gravitons, moduli, tachyons and other light fields. We compute the action and find that the quartic term for the tachyon is positive in the field definition where the tachyon has no derivative coupling to the radion. We study the evolution of isotropic, homogeneous configurations and find that typically the system is driven to regions where the calculation is no longer under control.