Realistic neutron star constraints on bosonic asymmetric dark matter
  It has been argued that the existence of old neutron stars excludes the
possibility of non-annihilating light bosonic dark matter, such as that arising
in asymmetric dark matter scenarios. If non-annihilating dark matter is
captured by neutron stars, the density will eventually become sufficient for
black hole formation. However, the dynamics of collapse is highly sensitive to
dark-matter self-interactions. Repulsive self-interactions, even if extremely
weak, can prevent black hole formation. We argue that self-interactions will
necessarily be present, and estimate their strength in representative models.
We also consider co-annihilation of dark matter with nucleons, which arises
naturally in many asymmetric dark matter models, and which again acts to
prevent black hole formation. We demonstrate how the excluded region of the
dark-matter parameter space shrinks as the strength of such interactions is
increased, and conclude that neutron star observations do not exclude most
realistic bosonic asymmetric dark matter models.
