Non-WIMP Candidates

TL;DR

This review explores various non-WIMP dark matter candidates, focusing on superWIMP and WIMPless models that naturally achieve the correct relic density through different mechanisms.

Contribution

It provides a comprehensive overview of non-WIMP dark matter candidates that share theoretical motivations with WIMPs and discusses their relic density mechanisms.

Findings

SuperWIMP candidates inherit relic density through decays.

WIMPless models maintain relic density via scaled mass and couplings.

These candidates expand the landscape of plausible dark matter particles.

Abstract

Non-WIMP dark matter candidates include particles motivated by minimality, candidates motivated by experimental anomalies, and exotic possibilities motivated primarily by the desire of clever iconoclasts to highlight how truly ignorant we are about the nature of dark matter. In this review, I discuss candidates that are not WIMPs, but nevertheless share the same theoretical motivations as WIMPs and also naturally have the correct relic density. There are two classes: superWIMP dark matter, where the desired relic density is inherited through decays, and WIMPless dark matter, where the dark matter's mass and couplings scale together to maintain the desired thermal relic density.