Quintessential kination and cold dark matter abundance

Abstract

The generation of a kination-dominated phase by a quintessential exponential model isinvestigated and the parameters of the model are restricted so that a number ofobservational constraints (originating from nucleosynthesis, the present acceleration of theuniverse and the dark-energy-density parameter) are satisfied. The decoupling ofa thermal cold dark matter particle during the period of kination is analysed,the relic density is calculated both numerically and semi-analytically and theresults are compared with each other. It is argued that the enhancement, withrespect to the standard paradigm, of the cold dark matter abundance can beexpressed as a function of the quintessential density parameter at the onset ofnucleosynthesis. We found that values of the latter quantity close to its upper boundrequire the thermal-averaged cross section times the velocity of the cold relic tobe almost three orders of magnitude larger than that needed in the standardscenario so that compatibility with the cold dark matter constraint is achieved.