Decay of multiple dark matter particles to dark radiation in different epochs does not alleviate the Hubble tension

TL;DR

Decaying dark matter models, including ensembles decaying into dark radiation at various epochs, do not resolve the Hubble tension due to strong observational constraints from CMB polarization and lensing.

Contribution

This study evaluates whether a dark matter ensemble decaying into dark radiation at different epochs can address the Hubble tension, finding it ineffective.

Findings

Decaying dark matter models are constrained by CMB polarization and lensing data.

Dark matter ensembles decaying into dark radiation do not alleviate the Hubble tension.

Observational constraints limit the impact of dark matter decay on cosmological tensions.

Abstract

Decaying cold dark matter (CDM) has been considered as a mechanism to tackle the tensions in the Hubble expansion rate and the clustering of matter. However, polarization measurements of the cosmic microwave background (CMB) severely constrain the fraction of dark matter decaying before recombination, and lensing of the CMB anisotropies by large-scale structure set strong constraints on dark matter decaying after recombination. Together, these constraints make an explanation of the Hubble tension in terms of decaying dark matter unlikely. In response to this situation, we investigate whether a dark matter ensemble with CDM particles decaying into free streaming dark radiation in different epochs can alleviate the problem. We find that it does not.