  It has been proposed that two resonances could coincide in the early universe
at temperatures $T \sim 0.2 ... 0.5$ GeV: one between two nearly degenerate
GeV-scale sterile neutrinos, producing a large lepton asymmetry through
freeze-out and decays; another between medium-modified active neutrinos and
keV-scale sterile neutrinos, converting the lepton asymmetry into dark matter.
Making use of a framework which tracks three sterile neutrinos of both
helicities as well as three separate lepton asymmetries, and scanning the
parameter space of the GeV-scale species, we establish the degree of
fine-tuning that is needed for realizing this scenario.

High Energy Physics - Phenomenology