The Effect of Massive Neutrinos on the Halo Spin Flip Phenomenon
  The halo spin flip refers to the phenomenon that the spin axes of dark matter
halos with masses above a certain threshold tend to be preferentially aligned
perpendicular to the hosting large-scale filaments, while low-mass halos tend
to have their spin axes aligned parallel to such structures. Extensive work has
so far been conducted to understand this phenomenon under the assumption of
cold dark matter and suggested that its origin should be closely related to the
nonlinear evolution of the halo angular momentum in the anisotropic cosmic web.
We present, for the first time, a numerical examination of this phenomenon
assuming the presence of massive neutrinos, finding a clear and robust
dependence of the threshold mass for the spin flip on the total neutrino mass.
Our physical explanation is that the presence of more massive neutrinos retard
the nonlinear evolution of the cosmic web, which in turn allows the halo spin
vectors to better retain their memories of the initial tidal interactions in
the nonlinear regime. Our finding implies that the statistical alignment of
halo spins with the large-scale structures can be in principle used as a probe
of the total neutrino mass.
