Inflationary Constraints on Late Time Modulus Dominated Cosmology

TL;DR

This paper derives constraints on the mass of a late-time modulus field in cosmology, linking it to inflationary parameters and reheating, often resulting in bounds stronger than the traditional cosmological moduli problem.

Contribution

It provides a novel relation connecting modulus mass, inflationary observables, and reheating characteristics, leading to new bounds on modulus mass in cosmological models.

Findings

Bounds on modulus mass can be significantly stronger than the cosmological moduli problem.

The derived relation constrains the modulus mass based on inflationary data and reheating details.

The analysis applies to a broad class of cosmological models with late-time modulus domination.

Abstract

We consider cosmological scenarios in which density perturbations are generated by the quantum fluctuations of the inflaton field at early times; the late time dynamics involves a modulus which first dominates the energy density of the universe and then decays to reheat the visible sector. By examining the evolution of energy density of the universe from the time of horizon exit of a pivot mode to the present day, and the fact that a modulus field decays via Planck suppressed interactions, we arrive at a relation which relates the mass of the modulus, inflationary observables/parameters and broad characteristics of the post inflationary reheating phase. When viewed together with generic expectations regarding reheating and the initial field displacement of the modulus after inflation, the relation gives a bound on the minimum mass of the modulus. For a large class of models, the bounds obtained (for the central values of Planck data) can be much stronger than the 'cosmological moduli problem' bound.