Abstract
The archetypal model for the recently discovered dark energy component of the universe is based on the existence of a scalar field whose dynamical evolution comes down today to a non-vanishing cosmological constant. In the past—before big-bang nucleosynthesis for that matter—that scalar field could have gone through a period of kination during which the universe has expanded at a much higher pace than what is currently postulated in the standard radiation dominated cosmology. I examine here the consequences of such a period of kination on the relic abundance of neutralinos and find that the latter could be much higher—by three orders of magnitude—than what is estimated in the canonical derivation. I shortly discuss the implications of this scenario for the dark matter candidates and their astrophysical signatures.
Highlights
The recent WMAP observations of the Cosmic Microwave Background (CMB) anisotropies [1], combined either with the determination of the relation between the distance of luminosity and the redshift of supernovae SNeIa [2], or with the large scale structure (LSS) information from galaxy and cluster surveys [3], give independent evidence for a cosmological average matter density of Ωm = 0.27 ± 0.04 [1]
We pay some attention to the difficulty of generating a kination–dominated expansion in the early universe together with a cosmological constant today [10]. We show that this difficulty may be circumvented depending on the potential V (Φ) that drives the evolution of the scalar field and we propose examples where quintessence boosts the expansion rate in the past while it still accounts for ΩΛ today
Following a suggestion by [12], we investigate in section III the effects of kination on the thermal decoupling of neutralinos and derive an approximate relation between their relic abundance Ωχ and their annihilation cross section in the presence of kination
Summary
A) Laboratoire de Physique Theorique LAPTH, B.P. 110, F-74941 Annecy-le-Vieux Cedex, France. b) Universite de Savoie, B.P. 1104, F-73011 Chambery Cedex, France. A) Laboratoire de Physique Theorique LAPTH, B.P. 110, F-74941 Annecy-le-Vieux Cedex, France. B) Universite de Savoie, B.P. 1104, F-73011 Chambery Cedex, France. The archetypal model for the recently discovered dark energy component of the universe is based on the existence of a scalar field whose dynamical evolution comes down today to a non–vanishing cosmological constant. In the past – before big–bang nucleosynthesis for that matter – that scalar field could have gone through a period of kination during which the universe has expanded at a much higher pace than what is currently postulated in the standard radiation dominated cosmology. I examine here the consequences of such a period of kination on the relic abundance of neutralinos and find that the latter could be much higher – by three orders of magnitude – than what is estimated in the canonical derivation. I shortly discuss the implications of this scenario for the dark matter candidates and their astrophysical signatures
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