Cosmological constraints on mass-varying dark matter

TL;DR

This paper investigates a cosmological model where dark matter mass varies over time, analyzing its effects on cosmic microwave background and large-scale structure data to constrain the transition epoch.

Contribution

It introduces and constrains a novel mass-varying dark matter model with a transition from zero to finite mass in the early Universe.

Findings

Power suppression in matter power spectrum below a certain scale.

Distinctive phase shift and power suppression in CMB angular spectrum.

Mild preference for mass-varying dark matter over ΛCDM in ACT data.

Abstract

As one of the fundamental unknowns of our Universe, the mass of dark matter remains to be a topic of great interest. We consider the possibility of a time-variation of the dark matter mass. We study the cosmological constraints on a model where the dark matter mass transitions from zero to a finite value in the early Universe. In this model, the matter power spectrum exhibits power suppression below a certain scale that depends on the epoch of transition, and the angular power spectrum of the cosmic microwave background shows a distinctive phase shift and power suppression at small scales. We use the latest cosmic microwave background data and the $S_8$ priors from weak lensing data to place a lower limit on the transition redshift. We also find that the data from the ACT show a mild preference for the mass-varying dark matter model over $\Lambda$CDM.