Tracking Quintessence and Cold Dark Matter Candidates

TL;DR

This paper explores a quintessence model with a kination phase, analyzing its effects on dark matter relic abundance and showing that certain dark matter candidates like gravitinos and axinos naturally fit within this framework.

Contribution

It introduces a model with a kination phase that addresses the coincidence problem and impacts dark matter relic abundance, providing new insights into dark matter candidates within this cosmological context.

Findings

Kination phase can be achieved early enough to solve the coincidence problem.

Relic abundance of WIMPs can be enhanced depending on temperature hierarchies.

Gravitinos and axinos are natural cold dark matter candidates in this model.

Abstract

We study the generation of a kination-dominated phase in the context of a quintessential model with an inverse-power-law potential and a Hubble-induced mass term for the quintessence field. The presence of kination is associated with an oscillating evolution of the quintessence field and the barotropic index. We find that, in sizeable regions of the parameter space, a tracker scaling solution can be reached sufficiently early to alleviate the coincidence problem. Other observational constraints originating from nucleosynthesis, the inflationary scale, the present acceleration of the universe and the dark-energy-density parameter can be also met. The impact of this modified kination-dominated phase on the thermal abundance of cold dark matter candidates is investigated too. We find that: (i) the enhancement of the relic abundance of the WIMPs with respect to the standard paradigm, crucially depends on the hierarchy between the freeze-out temperature and the temperature at which the extrema in the evolution of the quintessence field are encountered, and (ii) the relic abundance of e-WIMPs takes its present value close to the temperature at which the earliest extremum of the evolution of the quintessence field occurs and, as a consequence, both gravitinos and axinos arise as natural cold dark matter candidates. In the case of unstable gravitinos, the gravitino constraint can be satisfied for values of the initial temperature well above those required in the standard cosmology.