Speaker
Description
We investigate sub-GeV scalar dark matter embedded in a rich dark sector linking cosmology, neutrino physics, and astrophysical observables. The framework features a complex scalar dark matter candidate interacting via a Higgs-mixed mediator associated with the spontaneous breaking of a dark $U'(1)$ symmetry.
We first perform a numerical exploration of the scalar and dark matter sector and identify regions of parameter space where thermal production can reproduce the observed relic abundance while remaining consistent with existing constraints. We then extend the model by introducing a sterile neutrino and a pair of dark neutrinos charged under the broken symmetry. A large-scale numerical scan reveals viable regions where the mediator can decay before Big Bang Nucleosynthesis while simultaneously generating sub-eV active neutrino masses.
Finally, we discuss the phenomenological implications of this framework, including potential connections to the Galactic 511 keV line, and to gravitational-wave signals from the dark-sector phase transition.
