Dark matter properties through cosmic history

We perform the first test of dark matter (DM) stress-energy evolution through cosmic history, using microwave background measurements supplemented with baryon acoustic oscillation data and Hubble Space Telescope key project data. constrain DM equation state (EoS) in 8 redshift bins, its sound speed (shear) viscosity 9 finding no convincing evidence for non-$\Lambda$CDM values any bins. Despite this enlarged parameter space, are constrained relatively well at late times (due to inclusion CMB lensing), whereas EoS is most strongly around recombination. These results time level "coldness" required across various cosmological epochs both perturbative levels. show that simultaneously allowing dependence parameters shifts posterior abundance before recombination a higher value, while keeping present day similar $\Lambda$CDM value. This constant compared $\Lambda$CDM, suggesting time-dependent well-suited explore possible solutions persistent tensions within model. detailed comparison our previous study involving vanishing same datasets order explain physical mechanism behind these shifts.