Nonperturbative instabilities as a solution of the cosmological moduli problem

Abstract

It is widely accepted that moduli in the mass range $10\text{ }\text{ }\mathrm{eV}--{10}^{4}\text{ }\text{ }\mathrm{GeV}$ which start to oscillate with an amplitude of the order of the Planck scale either jeopardize successful predictions of nucleosynthesis or overclose the Universe. It is shown that the moduli problem can be relaxed by making use of parametric resonance. A new nonperturbative decay channel for moduli oscillations is discussed. This channel becomes effective when the oscillating field results in a net negative mass term for the decay products. This scenario allows for the decay of the moduli much before nucleosynthesis and, therefore, leads to a complete solution of the cosmological moduli problem.