# Cosmology in the presence of multiple light moduli

## TL;DR

This paper explores the cosmological effects of multiple light moduli fields in string theory, showing how their decay influences dark radiation and dark matter abundance, with implications for realistic cosmological models.

## Contribution

It analyzes the cosmology of multiple moduli fields with vacuum misalignment, highlighting the dilution of dark radiation and addressing dark matter overproduction issues.

## Key findings

- Dark radiation from heavier moduli is significantly diluted.
- Decay of heavier moduli can lead to dark matter overproduction.
- Prompt dark matter annihilation can produce realistic dark matter abundances.

## Abstract

The generic expectation in string/supergravity models is that there are multiple moduli fields with masses of the order of the supersymmetry breaking scale. We study the cosmology that arises as a result of vacuum misalignment of these moduli fields (in contrast to previous studies which mostly focussed on the single modulus case). We show that the dark radiation produced from the heavier moduli undergoes significant dilution. This happens even if there is a small splitting between the masses of the lightest and the heavier moduli. On the other hand, in the absence of fast annihilation processes decay of heavier moduli generically leads to overproduction of dark matter. We discuss a scenario where the problem can be addressed with a prompt dark matter annihilation to dark radiation. This can lead to realistic dark matter abundances, and the additional dark radiation produced as a result of this mechanism undergoes sufficient dilution as long as the annihilation is prompt.