Exploration/Observation and Research of Dark Matter

Dear Colleagues,

According to the standard cosmological ΛCDM model, Dark Matter (DM) should be a particle which is stable on cosmological time scales, cold (i.e., non-relativistic at the onset of galaxy formation), non-baryonic, neutral and weakly interacting. Strong premises for its existence come from the galactic, cluster and horizon scales, making the modified-gravity-based explanations of DM less likely. Various candidates for such a state exist in the literature, the most well-studied being the Weakly Interacting Massive Particles (WIMPs), which are postulated to have been in thermal equilibrium with the Standard Model (SM) particles after inflation. Once the rate of DM-SM reactions become smaller than the Hubble expansion rate of the Universe, the WIMPs freeze-out, i.e., drop out of the thermal equilibrium, leaving behind a relic density with the current value estimated by the Planck experiment to be 0.1200 ± 0.0012.

In recent years, the thermal relic DM paradigm has been heavily challenged by the results from direct-detection experiments, which systematically provide more stringent bounds on the strength of the interaction between dark and ordinary matter. Solutions to address this issue within the standard thermal-relic paradigm propose a multi-component DM from a large enough particle content beyond the SM which could make the cross sections probed in direct-detection experiments distinct from the cross sections affecting the freeze-out dynamics in the early universe. Another possible interpretation of these results is that DM consists of a secluded sector that is very feebly coupled to the SM. In this type of freeze-in model, the portal coupling of order 10^-10 allows the observed DM abundance to be produced out of equilibrium without ever equilibrating with the SM heat bath. Consequently, models of this type are usually completely invisible in the direct-detection experiments and require other detection/observational methods.

The aim of this Special Issue is to understand various cosmological aspects of DM, novel direct and indirect detection methods, and possible complementary astrophysical, cosmological and collider probes of DM.

Dr. Venus Keus
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Applied Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• particle dark matter
• multi-component dark matter
• novel direct and indirect detection methods
• collider signatures of dark matter
• complementarity of different dark matter probes