Evidences for Collisional Dark Matter In Galaxies?
  The more we go deep into the knowledge of the dark component which embeds the
stellar component of galaxies, the more we realize the profound interconnection
between them. We show that the scaling laws among the structural properties of
the dark and luminous matter in galaxies are too complex to derive from two
inert components that just share the same gravitational field. In this paper we
review the 30 years old paradigm of collisionless dark matter in galaxies. We
found that their dynamical properties show strong indications that the dark and
luminous components have interacted in a more direct way over a Hubble Time.
The proofs for this are the presence of central cored regions with constant DM
density in which their size is related with the disk lenghtscales. Moreover we
find that the quantity $\rho_{DM}(r,L,R_D) \rho_\star (r,L,R_D)$ shows, in all
objects, peculiarities very hardly explained in a collisionless DM scenario.
