IMSc Webinar

Developments in dark matter relic abundance calculations

Andrzej Hryczuk

National Centre for Nuclear Research, Warsaw

Among viable dark matter production mechanisms the thermal freeze-out stands out as the most natural and best motivated one. In the usual theoretical approach to the determination of its thermal relic abundance the assumption of local thermal equilibrium is
made. But is this assumption always justified? In this talk I will first introduce the topic and then address this question. Then I will discuss how to go beyond this assumption and introduce DRAKE — a numerical precision tool that can trace not only the dark
matter relic density, but also its velocity dispersion and full phase space distribution function. I will review the general motivation for this approach and, for illustration, highlight three concrete classes of models where kinetic and chemical decoupling are
intertwined in a way that can impact the value of the relic density by as much as an order of magnitude: i) dark matter annihilation via a narrow resonance, ii) Sommerfeld-enhanced annihilation and iii) `forbidden' annihilation to final states that are
kinematically inaccessible at threshold. Finally, I will comment on most recent developments in the topic.