Linear scale bounds on dark matter--dark radiation interactions and
  connection with the small scale crisis of cold dark matter
  One of the open questions in modern cosmology is the small scale crisis of
the cold dark matter paradigm. Increasing attention has recently been devoted
to self-interacting dark matter models as a possible answer. However, solving
the so-called "missing satellites" problem requires in addition the presence of
an extra relativistic particle (dubbed dark radiation) scattering with dark
matter in the early universe. Here we investigate the impact of different
theoretical models devising dark matter dark radiation interactions on large
scale cosmological observables. We use cosmic microwave background data to put
constraints on the dark radiation component and its coupling to dark matter. We
find that the values of the coupling allowed by the data imply a cut-off scale
of the halo mass function consistent with the one required to match the
observations of satellites in the Milky Way.
