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.
Chen et al. (2025) studied this question.