Ultra-light dark matter
By Elisa G. M. Ferreira. The Astronomy and Astrophysics Review, 2020
431 citations recorded by the source corpus.
Ultra-light dark matter is a class of dark matter models (DM), where DM is composed by bosons with masses ranging from $$10^{-24}\, \mathrm {eV}< m < \mathrm {eV}$$ 10 - 24 eV < m < eV . These models have been receiving a lot of attention in the past few years given their interesting property of forming a Bose–Einstein condensate (BEC) or a superfluid on galactic scales. BEC and superfluidity are some of the most striking quantum mechanical phenomena that manifest on macroscopic scales, and upon condensation, the particles behave as a single coherent state, described by the wavefunction of the condensate. The idea is that condensation takes place inside galaxies while outside, on large scales, it recovers the successes of $$\varLambda $$ Λ CDM. This wave nature of DM on galactic scales that arise upon condensation can address some of the curiosities of the behaviour of DM on small-scales. There are many models in the literature that describe a DM component that condenses in galaxies. In this review, we are going to describe those models, and classify them into three classes, according to the different non-linear evolution and structures they form in galaxies: the fuzzy dark matter (FDM), the self-interacting fuzzy dark matter (SIFDM), and the DM superfluid. Each of these classes comprises many models, each presenting a similar phenomenology in galaxies. They also include some microscopic models like the axions and axion-like particles. To understand and describe this phenomenology in galaxies, we are going to review the phenomena of BEC and superfluidity that arise in condensed matter physics, and apply this knowledge to DM. We describe how ULDM can potentially reconcile the cold DM picture with the small-scale behaviour. These models present a rich phenomenology that is manifest in different astrophysical consequences. We review here the astrophysical and cosmological tests used to constrain those models, together with new and future observations that promise to test these models in different regimes. For the case of the FDM class, the mass where this model has an interesting phenomenology on small-scales $$ \sim 10^{-22}\, \mathrm {eV}$$ ∼ 10 - 22 eV , is strongly challenged by current observations. The parameter space for the other two classes remains weakly constrained. We finalize by showing some predictions that are a consequence of the wave nature of this component, like the creation of vortices and interference patterns, that could represent a smoking gun in the search of these rich and interesting alternative class of DM models.
Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/2449abdb31f12b95178038fd30fb9810a2a93ee0
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Citations in the corpus
- New physics from the polarized light of the cosmic microwave background (2022, background): “There exists a distinct possibility that a parity-violating pseudoscalar field, χ , is responsible for dark matter and dark energy 71,72 .”
- Resolving the Hubble tension with new early dark energy (2020, background): “We observe that the trigger mass lies between a typical mass scale for ultralight DM (∼ 10−22 eV) and quintessence DE (∼ 10−33 eV), both of which can be realized in axion scenarios [126, 127], where the mass is protected by a weakly broken shift symmetry.”