Abstract
Despite the astonishing success of standard ΛCDM cosmology, there is mounting evidence for a tension with observations at small and intermediate scales. We introduce a simple model where both cold dark matter (DM) and sterile neutrinos are charged under a new U(1)X gauge interaction. The resulting DM self-interactions resolve the tension with the observed abundances and internal density structures of dwarf galaxies. At the same time, the sterile neutrinos can account for both the small hot DM component favored by cosmological observations and the neutrino anomalies found in short-baseline experiments.
Highlights
This requires an effective number of additional neutrino species ∆Neff and an effective HDM mass of [37]
We demonstrate that all aforementioned problems of standard cosmology are resolved by coupling both CDM and sterile neutrinos, the latter automatically being promoted to the desired HDM component, to a U (1)X gauge boson of O (MeV) mass
We further assume that the U (1)X is spontaneously broken at the MeV scale by the vacuum expectation value (VEV) vΘ of a complex Higgs field Θ, which is a representation (1, 0, 2XνR) under SU (2)L × U (1)Y × U (1)X, while the Higgs field φ responsible for the electroweak symmetry breaking is a (2, 1/2, 0)
Summary
We further assume that the U (1)X is spontaneously broken at the MeV scale by the vacuum expectation value (VEV) vΘ of a complex Higgs field Θ, which is a representation (1, 0, 2XνR) under SU (2)L × U (1)Y × U (1)X , while the Higgs field φ responsible for the electroweak symmetry breaking is a (2, 1/2, 0). Another complex scalar ξ, with charges (1, 0, XνR) and VEV vξ < vΘ, is introduced to enable active-sterile neutrino mixing. We assume the couplings of the additional portal terms |φ|2|ξ|2 and |Θ|2|ξ|2 to be negligibly small
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