Resolution of Hagedorn singularity in superstrings with gravito-magnetic fluxes

TL;DR

This paper demonstrates how asymmetric fluxes in superstring backgrounds can resolve Hagedorn singularities, leading to a stable thermal phase with unique duality properties and novel massless states.

Contribution

It introduces a method to eliminate Hagedorn instabilities in superstrings using gravito-magnetic fluxes and reveals a temperature duality symmetry in the free energy.

Findings

Hagedorn-like instabilities are avoided for certain chemical potentials.

The free energy exhibits a temperature duality symmetry, ${ m F}(T/T_H)={T^2 ext{}/T_H^2} { m F}(T_H/T)$.

Extra massless scalars and charged states appear at the self-dual temperature.

Abstract

We consider closed type II and orientifold backgrounds where supersymmetry is spontaneously broken by asymmetric geometrical fluxes. We show that these can be used to describe thermal ensembles with chemical potentials associated to "gravito-magnetic" fluxes. The thermal free energy is computed at the one-loop string level, and it is shown to be free of the usual Hagedorn-like instabilities for a certain choice of the chemical potentials. In the closed string gravitational sector, as well as in the open string matter sector of the proposed orientifold construction, the free energy turns out to have "Temperature duality" symmetry, ${\cal F}(T/T_H)={T^2\over T_H^2} {\cal F}(T_H/T)$, which requires interchanging the space-time spinor representations $S\leftrightarrow C$. For small temperatures, $T\to 0$, the anti-spinor $C$ decouples from the spectrum while for large temperatures, $T\to \infty$, the spinor $S$ decouples. In both limits the free energy vanishes, as we recover a conventional type II superstring theory. At the self dual point $T=T_H$, the thermal spectra of $S$ and $C$ are identical. Moreover, there are extra massless scalars in the adjoint representation of an SO(4) non-abelian gauge symmetry in the closed-string sector, and open-string massless states charged simultaneously under both the Chan-Paton and the closed-string SO(4) gauge group.