Gravitino cosmology with a very light neutralino

TL;DR

This paper investigates how very light neutralinos, compatible with experiments and astrophysics, influence cosmology, especially Big Bang nucleosynthesis, and finds they are supported by current observations.

Contribution

It provides the first detailed analysis of cosmological constraints on very light neutralinos considering gravitino effects, showing they are favored by data.

Findings

Very light neutralinos are consistent with astrophysical and cosmological bounds.

Cosmological constraints from Big Bang nucleosynthesis favor very light neutralinos.

Gravitino effects do not exclude but support the viability of light neutralinos.

Abstract

It has been shown that very light or even massless neutralinos are consistent with all current experiments, given non-universal gaugino masses. Furthermore, a very light neutralino is consistent with astrophysical bounds from supernov{\ae} and cosmological bounds on dark matter. Here we study the cosmological constraints on this scenario from Big Bang nucleosynthesis taking gravitinos into account and find that a very light neutralino is even favoured by current observations.