Relativistic bias in neutrino cosmologies
  Halos and galaxies are tracers of the underlying dark matter structures.
While their bias is well understood in the case of a simple Universe composed
dominantly of dark matter, the relation becomes more complex in the presence of
massive neutrinos. Indeed massive neutrinos introduce rich dynamics in the
process of structure formation leading to scale-dependent bias. We study this
process from the perspective of general relativity employing a simple spherical
collapse model. We find a characteristic signature at the neutrino
free-streaming scale in addition to a large-scale feature from general
relativity. The scale-dependent halo bias opposes the suppression in the matter
distribution due to neutrino free-streaming and leads to corrections of a few
percent in the halo power spectrum. It is not only sensitive to the sum of the
neutrino-masses, but respond to the individual masses. Accurate models for the
neutrino bias are a crucial ingredient for the future data analysis and play an
important role in constraining the neutrino masses.
