Attraction to a radiation-like era in early superstring cosmologies

TL;DR

This paper investigates how quantum and thermal corrections in early superstring cosmologies influence the universe's evolution, revealing attractor solutions that resemble radiation-dominated eras or lead to a Big Crunch, with limited inflation.

Contribution

It provides a detailed analysis of the backreaction effects of quantum and thermal corrections in superstring cosmologies, identifying conditions for different late-time behaviors.

Findings

Cosmological solutions tend to attract to radiation-like or Big Crunch trajectories.

Periods of accelerated expansion can occur but are insufficient for inflation.

Quantum and thermal effects significantly influence early universe evolution.

Abstract

Starting from an initial classical four dimensional flat background of the heterotic or type II superstrings, we are able to determine at the string one-loop level the quantum corrections to the effective potential due to the spontaneous breaking of supersymmetry by "geometrical fluxes". Furthermore, considering a gas of strings at finite temperature, the full "effective thermal potential" is determined, giving rise to an effective non-trivial pressure. The backreaction of the quantum and thermal corrections to the space-time metric as well as to the moduli fields induces a cosmological evolution that depends on the early time initial conditions and the number of spontaneously broken supersymmetries. We show that for a whole set of initial conditions, the cosmological solutions converge at late times to two qualitatively different trajectories: They are either attracted to (i) a thermal evolution similar to a radiation dominated cosmology, implemented by a coherent motion of some moduli fields, or to (ii) a "Big Crunch" non-thermal cosmological evolution dominated by the non-thermal part of the effective potential or the moduli kinetic energy. During the attraction to the radiation-like era, periods of accelerated cosmology can occur. However, they do not give rise to enough inflation (e-fold < 0.2) for the models we consider, where N>1 supersymmetry is spontaneously broken to N=0.