Evolving Dark Energy or Evolving Dark Matter?

Abstract

We show that the latest empirical constraints on cosmology, from a combination of DESI, CMB and supernova data, can be accounted for if a small component of dark matter has an evolving and oscillating equation of state within $-1<w<1$. From a fundamental physics perspective, this interpretation is more appealing than an evolving phantom dark energy with $w<-1$, which violates the null energy condition.

v2: 21 pages; discussions in Sec.4 and Sec.5 extended, and other minor revisions