Dynamics of neutrino lumps in growing neutrino quintessence
  We investigate the formation and dissipation of large scale neutrino
structures in cosmologies where the time evolution of dynamical dark energy is
stopped by a growing neutrino mass. In models where the coupling between
neutrinos and dark energy grows with the value of the scalar cosmon field, the
evolution of neutrino lumps depends on the neutrino mass. For small masses the
lumps form and dissolve periodically, leaving only a small backreaction of the
neutrino structures on the cosmic evolution. This process heats the neutrinos
to temperatures much above the photon temperature such that neutrinos acquire
again an almost relativistic equation of state. The present equation of state
of the combined cosmon-neutrino fluid is very close to -1. In contrast, for
larger neutrino masses the lumps become stable. The highly concentrated
neutrino structures entail a large backreaction similar to the case of a
constant neutrino-cosmon coupling. A present average neutrino mass of around
0.5 eV seems so far compatible with observation. For masses lower than this
value, neutrino induced gravitational potentials remain small, making the lumps
difficult to detect.
