Can unstable relics save pure Cold Dark Matter?

TL;DR

This paper explores whether unstable relic particles in extensions of the electroweak standard model can address the small-scale power spectrum issues in the Cold Dark Matter model by injecting non-thermal radiation.

Contribution

It investigates the feasibility of using late decaying particles to modify the power spectrum within certain standard model extensions, considering cosmological and astrophysical constraints.

Findings

Unstable relics can potentially reconcile CDM predictions with observations.

Cosmological bounds limit the parameter space for decaying particles.

Extensions of the electroweak model can accommodate such relics under specific conditions.

Abstract

The standard CDM model fails to describe the power spectrum of fluctuations since it gives too much power at small scales. Among other possible improvements, it has been suggested that an agreement with observations can be achieved with the addition of a late decaying particle, through the injection of non-thermal radiation and the consequent increase of the horizon length at the equivalence time. We analyze the possibility of implementing this idea in some extensions of the electroweak standard model, discussing the cosmological and astrophysical bounds to which these schemes are subject.