Limits in late time conversion of cold dark matter into dark radiation

TL;DR

This paper explores the possibility of late-time conversion of cold dark matter into dark radiation during structure formation, analyzing its effects and constraints within cosmological models, and suggesting it as a viable hypothesis for future testing.

Contribution

It introduces a phenomenological model for dark matter conversion inspired by supernova neutrino emission, and assesses its impact on cosmological constraints and structure formation.

Findings

No strong preference for dark matter conversion over standard DM

Best fit within 1c3 of standard model parameters

Potential to address small-scale structure discrepancies

Abstract

Structure formation creates high temperature and density regions in the Universe that allow the conversion of matter into more stable states, with a corresponding emission of relativistic matter and radiation. An example of such a mechanism is the supernova event, that releases relativistic neutrinos corresponding to 99% of the binding energy of remnant neutron star. We take this phenomena as a starting point for an assumption that similar processes could occur in the dark sector, where structure formation would generate a late time conversion of cold dark matter into a relativistic form of dark matter. We performed a phenomenological study about the limits of this conversion, where we assumed a transition profile that is a generalized version of the neutrino production in supernovae events. With this assumption, we obtained an interesting modification for the constraint over the cold dark matter density. We show that when comparing with the standard \Lambda CDM cosmology, there is no preference for conversion, although the best fit is within 1\sigma\ from the standard model best fit. The methodology and the results obtained qualify this conversion hypothesis, from the large scale structure point of view, as a viable and interesting model to be tested in the future with small scale data, and mitigate discrepancies between observations at this scale and the pure cold dark matter model.