Quintessence and the Relic Density of Neutralinos
Pierre Salati
TL;DR
The paper investigates how an early-period kination, sourced by quintessence, modifies the expansion history of the universe before BBN and, in turn, the relic density of neutralino dark matter. It develops an approximate relation between the relic abundance and the annihilation cross section in a kination-dominated era, discusses the overshoot problem, and proposes quintessence potentials that can reconcile a past kination phase with today’s near-constant dark energy density. The key result is that the neutralino relic density can be enhanced by up to roughly three orders of magnitude compared to the standard radiative-era calculation, with significant implications for dark matter phenomenology and astrophysical signatures. The work highlights the importance of early-universe expansion history in constraining WIMP candidates and motivates careful consideration of quintessence–dark-energy interactions in relic-density calculations, potentially altering detection prospects.
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. This new version contains a discussion - see section 2 - of the overshooting problem and offers perspectives to reconcile an initial period of violent kination with the existence of a cosmological constant today.