Quintessential kination and thermal production of gravitinos and axinos

Abstract

The impact of a kination-dominated phase generated by a quintessential exponential model on the thermal abundance of gravitinos and axinos is investigated. We find that their abundances become proportional to the transition temperature from the kination to the radiation era; since this temperature is significantly lower than the initial ("reheating") temperature, the abundances decrease with respect to their values in the standard cosmology. For values of the quintessential energy-density parameter close to its upper bound, on the eve of nucleosynthesis, we find the following: (i) for unstable gravitinos, the gravitino constraint is totally evaded; (ii) If the gravitino is stable, its thermal abundance is not sufficient to account for the cold dark matter of the universe; (iii) the thermal abundance of axinos can satisfy the cold dark matter constraint for values of the initial temperature well above those required in the standard cosmology. A novel calculation of the axino production rate by scatterings at low temperature is also presented.

Quintessential Kination and Thermal Production of SUSY e-WIMPs

“…(1) and (2) numerically [10]. However, we can get a clear picture of the results via semi-analytical estimates [10]. In the high T regime (T I ≫ T C and T KR ≫ T C ) we find, within a 10% accuracy, that:…”

“…The impact of the KD phase on the relic density Ω χ h 2 = 2.748 × 10 8 Y 0 χ m χ /GeV can be found by solving Eqs. (1) and (2) numerically [10]. However, we can get a clear picture of the results via semi-analytical estimates [10].…”

“…In the case ofã, where Ωãh 2 takes cosmologically interesting values for T ≪ m i , Cã has been calculated numerically in Ref. [10]. In the latter case, Γ i with i =g,q andB are taken into account, also, using the formulas of Refs.…”

“…[10], we reconsider the creation of a quintessential kination scenario (QKS) in the context of the exponential quintessential model [5,11], and investigate its impact on the thermal production of e-WIMPs.…”

Classical and quantum cosmology with two perfect fluids: stiff matter and radiation

“…As the energy density of the stiff matter [9], in the same gauge, is proportional to 1/a(t) 6 , there must have been a time before the radiation in which the stiff matter dominated. In fact, the abundance of particles produced after the Big Bang due to expansion and cooling of the Universe is an implication of the presence of this fluid with α = 1 at this stage [10][11][12][13][14][15][16].…”