Captures of Hot and Warm Sterile Antineutrino Dark Matter on EC-decaying
  Ho-163 Nuclei
  Capturing low-energy electron antineutrinos on radioactive Ho-163 nuclei,
which decay into Dy-163 via electron capture (EC), is a noteworthy opportunity
to detect relic sterile antineutrinos. Such hypothetical particles are more or
less implied by current experimental and cosmological data, and they might be a
part of hot dark matter or a candidate for warm dark matter in the Universe.
Using the isotope Ho-163 as a target and assuming reasonable active-sterile
antineutrino mixing angles, we calculate the capture rate of relic electron
antineutrinos against the corresponding EC-decay background in the presence of
sterile antineutrinos at the sub-eV or keV mass scale. We show that the
signature of hot or warm sterile antineutrino dark matter should in principle
be observable, provided the target is big enough and the energy resolution is
good enough.
