title: Dark radiation alleviates problems with dark matter halos.
abstract: We show that a scalar and a fermion charged under a global U(1) symmetry can not only explain the existence and abundance of dark matter (DM) and dark radiation (DR), but can also imbue DM with improved scattering properties at galactic scales, while remaining consistent with all other observations. Delayed DM-DR kinetic decoupling eases the missing satellites problem, while scalar-mediated self-interactions of DM ease the cusp versus core and too big to fail problems. In this scenario, DM is expected to be pseudo-Dirac and have a mass 100 keV ≲ m(χ) ≲ 10 GeV. The predicted DR may be measurable using the primordial elemental abundances from big bang nucleosynthesis, and using the cosmic microwave background.
authors.affiliation: International Centre for Theoretical Physics, Strada Costiera 11, 34014 Trieste, Italy.
authors.forename: Xiaoyong
authors.initials: X
authors.lastname: Chu
authors.affiliation: International Centre for Theoretical Physics, Strada Costiera 11, 34014 Trieste, Italy.
authors.forename: Basudeb
authors.initials: B
authors.lastname: Dasgupta