Mixed Dark Matter models with a non-thermal hot component: fluctuation evolution

Abstract

We calculate the linear evolution for a class of mixed dark matter models, where the hot component derives from the decay of a heavier particle (CntHDM models). These models differ from ordinary mixed models based on massive neutrinos (CHDM models), for which the hot component has a phase space distribution which derives from a thermal one. In CntHDM models the density of the hot component and the derelativisation redshift of its quanta are indipendent parameters. In this work we provide the spectra for a number of CntHDM models, and compare them with CDM and CHDM spectra. If PQ symmetry and SUSY simultaneously hold, the lightest standard neutralino can be expected to decay into axino and photon. We briefly summarise the features of this particle model which gives rise to the cosmological framework discussed here, as a fairly generic consequence. Other frameworks which lead to similar models are also briefly discussed.