  We study the phase transition of a system of self-gravitating neutrinos in
the presence of a large radiation density background in the framework of the
Thomas-Fermi model. We show that, by cooling a non-degenerate gas of massive
neutrinos below some critical temperature, a condensed phase emerges,
consisting of quasi-degenerate supermassive neutrino stars. These compact dark
objects could play an important role in structure formation in this universe,
as they might in fact provide the seeds for galactic nuclei and quasi-stellar
objects.
