DESI-Like Hubble Expansion From Staged Symmetry Breaking - Zachary Hoelscher

Описание: The Dark Energy Spectroscopic Instrument (DESI) second data release shows a moderate preference for dark energy with a time-varying equation of state parameter, suggesting that the standard Lambda CDM model may need to be revised. In particular, DESI favors dark energy whose equation of state parameter can drop below -1, violating the null energy condition. Chen and Loeb have recently suggested that this violation may be avoided if a subcomponent of the dark matter possesses a time-dependent equation of state. In this work, we present a realization of that idea which can be regarded as a more natural effective field theory. We show that such a construction not only yields dark matter with a time-varying equation of state parameter, but also naturally produces a self-interacting dark matter candidate with a velocity-dependent cross section as a consequence of gauge invariance. The second feature is relevant for addressing tensions between Lambda CDM and observations of small-scale structure, particularly the diversity of galactic rotation curves. We also discuss extending the model to a scenario where dark energy is a quintessence field, rather than a cosmological constant, which serves to prevent the formation of a cosmological horizon at late times.