Sterile Neutrinos as Dark Matter: From Production to Predictions

Sterile neutrinos with masses of a few keV are very
well-motivated Dark Matter candidates. However, even though they have the
perfect properties for that job, it is unclear how to produce them in the
early Universe. In this talk, I will mainly focus on how to make this
production happen in the early Universe. While several proposals exist in
the literature, the production aspect unfortunately suffers from several
incorrect or at least oversimplified statements (e.g., that keV sterile
neutrino Dark Matter would usually be ‘warm’). I will make an attempt to
explain parts of the issues and how to resolve them, which ultimately
leads to means to distinguish the different mechanisms via their impact on
cosmic structure formation. While lab experiments are not well-suited to
probe this type of Dark Matter candidate, cosmology and astrophysics
provide the tools to do so. The whole talk is supposed to be more
pedagogical than technical, so I will avoid heavy formula whereever
possible.