Dark matter (DM) makes up most of the Universe’s matter, but its particle nature remains largely unkown. While large-scale observations strongly support a cold DM paradigm, DM may not be strictly collisionless. This motivates the concept of self-interacting DM, where DM scatterings help reconcile small-scale observations. If these collisions also dissipate energy (e.g. by radiating hidden particles), halo cooling and denser structures could ensue—a possibility rarely addressed in depth. One major aim here is to develop a comprehensive theoretical framework for such dissipative SIDM processes, and to investigate, whether they yield observable astrophysical or cosmological signals.
On the experimental side, as null searches for electroweak mass DM persist and attention shifts to sub-GeV DM, the experiments increasingly rely on rare secondary, but irreducible effects—for instance, the emission of soft photons (bremsstrahlung) or electrons (Migdal effect) during DM–nucleus scattering. These subtle processes can reveal energy transfers of lighter DM candidates, that otherwise go undetected. However, many existing calculations use simplifying assumptions that may fail under more general conditions. Our project seeks to put these direct-detection signals on solid footing, in a way that the full quantum and atomic/solid-state physics is captured. This will reinforce the interpretation of experimentally reported results.
By unifying advanced astrophysical and experimental approaches, the aim is to broaden the search window for DM and to equip the community with robust tools to interpret an eventual DM signal.
