Cosmic Equation of State, Quintessence and Decaying Dark Matter

TL;DR

Decaying dark matter can alter the universe's equation of state, and models combining this decay with quintessence or cosmological constant fit supernova data better than stable dark matter models.

Contribution

This paper demonstrates that decaying dark matter models can produce an effective equation of state less than -1, aligning with supernova observations and extending previous cosmological models.

Findings

Decaying dark matter models are consistent with high redshift supernova data.

Effective w_q can be less than -1 in models with decaying dark matter.

Such models fit supernova data better than stable dark matter or standard quintessence models.

Abstract

If CDM particles decay and their lifetime is comparable to the age of the Universe, they can modify its equation of state. By comparing the results of numerical simulations with high redshift SN-Ia observations we show that this hypothesis is consistent with present data. Fitting the simplest quintessence models with constant $w_q$ to data leads to $w_q \lesssim -1$. We show that a universe with a cosmological constant or quintessence matter with $w_q \sim -1$ and a decaying Dark Matter has an effective $w_q < -1$ and fits SN data better than stable CDM or quintessence models with $w_q > -1$.