Non-perturbative Temperature Instabilities in N=4 Strings

TL;DR

This paper investigates high-temperature instabilities in N=4 superstring theories, identifying non-perturbative tachyonic modes, analyzing phase transitions involving five-brane condensation, and describing the resulting supersymmetry breaking and topological phases.

Contribution

It provides a universal effective potential for all N=4 superstring instabilities and details the phase transition to a topological phase with supersymmetry restoration.

Findings

Identification of three non-perturbative tachyonic modes

Description of a high-temperature phase transition involving five-branes

Analysis of supersymmetry breaking and topological phases at infinite temperature

Abstract

We derive a universal thermal effective potential, which describes all possible high-temperature instabilities of the known N=4 superstrings, using the properties of gauged N=4 supergravity. These instabilities are due to three non-perturbative thermal dyonic modes, which become tachyonic in a region of the thermal moduli space. The latter is described by three moduli, s,t,u, which are common to all non-perturbative dual-equivalent strings with N=4 supersymmetry in five dimensions: the heterotic on T^4xS^1, the type IIA on K3xS^1, the type IIB on K3xS^1 and the type I on T^4x S^1. The non-perturbative instabilities are analysed. These strings undergo a high-temperature transition to a new phase in which five-branes condense. This phase is described in detail, using both the effective supergravity and non-critical string theory in six dimensions. In the new phase, supersymmetry is perturbatively restored but broken at the non-perturbative level. In the infinite-temperature limit the theory is topological with an N=2 supersymmetry based on a topologically non-trivial hyper-Kahler manifold.