  At high densities in compact astrophysical sources, the coherent forward
scattering of neutrinos onto each other is responsible for making the flavor
evolution non-linear. Under the assumption of spherical symmetry, we present
the first simulations tracking flavor transformation in the presence of
neutrino-neutrino forward scattering, neutral and charged current collisions
with the matter background, as well as neutrino advection. We find that,
although flavor equipartition could be one of the solutions, it is not a
generic outcome, as often postulated in the literature. Intriguingly, the
strong interplay between flavor conversion, collisions, and advection leads to
a spread of flavor conversion across the neutrino angular distributions and
neighboring spatial regions. Our simulations show that slow and fast flavor
transformation can occur simultaneously. In the light of this, looking for
crossings in the electron neutrino lepton number as a diagnostic tool of the
occurrence of flavor transformation in the high-density regime is a limiting
method.
