Item

Abstract

We propose a novel mechanism to generate sterile neutrinos ν_s in the early Universe, by converting ordinary neutrinos ν_α in scattering processes ν_sν_α → ν_sν_s. After initial production by oscillations, this leads to an exponential growth in the ν_s abundance. We show that such a production regime naturally occurs for self-interacting ν_s, and that this opens up significant new parameter space where νs make up all of the observed dark matter. Our results provide strong motivation to further push the sensitivity of X-ray line searches, and to improve on constraints from structure formation.