Dark matter production in the early Universe: beyond the thermal WIMP paradigm

TL;DR

This paper reviews various dark matter production mechanisms beyond the standard thermal WIMP paradigm, emphasizing non-thermal relics, mixed SUSY/axion candidates, and alternative models in light of recent experimental constraints.

Contribution

It provides a comprehensive overview of both thermal and non-thermal dark matter models, highlighting the cosmological properties of mixed SUSY/axion candidates and alternative scenarios.

Findings

Constraints from LHC and dark matter searches limit WIMP models.

Mixed SUSY/axion dark matter candidates exhibit rich cosmological behaviors.

Non-thermal relics offer viable dark matter solutions beyond WIMPs.

Abstract

Increasingly stringent limits from LHC searches for new physics, coupled with lack of convincing signals of weakly interacting massive particle (WIMP) in dark matter searches, have tightly constrained many realizations of the standard paradigm of thermally produced WIMPs as cold dark matter. In this article, we review more generally both thermally and non-thermally produced dark matter (DM). One may classify DM models into two broad categories: one involving bosonic coherent motion (BCM) and the other involving WIMPs. BCM and WIMP candidates need, respectively, some approximate global symmetries and almost exact discrete symmetries. Supersymmetric axion models are highly motivated since they emerge from compelling and elegant solutions to the two fine-tuning problems of the Standard Model: the strong CP problem and the gauge hierarchy problem. We review here non-thermal relics in a general setup, but we also pay particular attention to the rich cosmological properties of various aspects of mixed SUSY/axion dark matter candidates which can involve both WIMPs and BCM in an interwoven manner. We also review briefly a panoply of alternative thermal and non-thermal DM candidates.