Primordial dark matter halos from fifth forces
  We argue that primordial dark matter halos could be generated during
radiation domination by long range attractive forces stronger than gravity. In
this paper we derive the conditions under which these structures could dominate
the dark matter content of the Universe while passing microlensing constraints
and cosmic microwave background energy injection bounds. The dark matter
particles would be clumped in objects in the solar mass range with typical
sizes of the order of the solar system. Consequences for direct dark matter
searches are important.
