Finite temperature effects in modular cosmology

Abstract

We revisit the cosmological history in the presence of light moduli by including possible thermal effects in the scalar potential. The well known cosmological moduli problem regards initial energy stored in the moduli due to a misalignment from its final position during inflation. We show that finite temperature corrections to the scalar potential, in general, induce similar effects and these are likely to overcome the ones from the misalignment. This changes important parameters like the preferred window for the numbers of e-fold during inflation and the final reheating temperature in a model-dependent manner. The general implications are a longer late modulus dominated epoch and a larger final reheating temperature. We explore all the discussed elements in type-IIB superstring Large Volume Compactification with a Kähler inflationary scenario, where zero temperature results are known. An instability analysis, using a Floquet approach, is also performed for this explicit case finding strong indications of possible oscillon production around a nearly universal normalized critical temperature, where the Floquet exponents show a divergent behaviour.