Time- and space-varying neutrino masses from soft topological defects
  We study the formation and evolution of topological defects that arise in the
post-recombination phase transition predicted by the gravitational neutrino
mass model in [Dvali, Funcke, 2016]. In the transition, global skyrmions,
monopoles, strings, and domain walls form due to the spontaneous breaking of
the neutrino flavor symmetry. These defects are unique in their softness and
origin, as they appear at a very low energy scale, they only require Standard
Model particle content, and they differ fundamentally depending on the Majorana
or Dirac nature of the neutrinos. One of the observational signatures is the
time- and space-dependence of the neutrino mass matrix, which could be
observable in future experiments such as DUNE or in the event of a near-future
galactic supernova explosion. Already existing data rules out parts of the
parameter space in the Majorana case. The detection of this effect could shed
light onto the open question of the Dirac versus Majorana neutrino nature.
