Decaying warm dark matter and structure formation

TL;DR

This paper explores how decaying warm dark matter influences structure formation, comparing it to cold dark matter models, and finds it can be a viable alternative with distinct small-scale effects.

Contribution

It introduces a decaying warm dark matter model motivated by particle physics, analyzing its impact on structure formation through simulations and comparing it to standard models.

Findings

Decaying warm dark matter affects small-scale structure formation.

The model provides a viable alternative to the standard bcdm paradigm.

Predictions differ significantly on small scales.

Abstract

We examine the cosmology of warm dark matter (WDM), both stable and decaying, from the point of view of structure formation. We compare the matter power spectrum associated to WDM masses of 1.5 keV and 0.158 keV, with that expected for the stable cold dark matter $\Lambda$CDM$\equiv$SCDM paradigm, taken as our reference model. We scrutinize the effects associated to the warm nature of dark matter, as well as the fact that it decays. The decaying warm dark matter (DWDM) scenario is well-motivated, emerging in a broad class of particle physics theories where neutrino masses arise from the spontaneous breaking of a continuous global lepton number symmetry. The majoron arises as a Nambu-Goldstone boson, and picks up a mass from gravitational effects, that explicitly violate global symmetries. The majoron necessarily decays to neutrinos, with an amplitude proportional to their tiny mass, which typically gives it cosmologically long lifetimes. Using N-body simulations we show that our DWDM picture leads to a viable alternative to the $\Lambda$CDM scenario, with predictions that can differ substantially on small scales.