Self-interacting dark matter from late decays and the H0 tension

Abstract

We study the production mechanism of self-interacting dark matter based on decays of a messenger WIMP-like state into dark matter and dark radiation taking place after the recombination. Such transition leads to a mild relaxation of the Hubble tension while simultaneously having the potential of addressing small-scale structure problems of ?CDM. We illustrate the mechanism within a Higgs portal dark matter model which we find to be a promising avenue.