The 21cm Absorption Line and Axion Quark Nugget Dark Matter Model
  We argue that dark matter in the form of macroscopically large nuggets of
standard model quarks and antiquarks can help to alleviate the tension between
standard model cosmology and the recent EDGES observation of a stronger than
anticipated 21 cm absorption feature. The effect occurs as a result of the
thermal emission from quark nugget dark matter at early times and at energies
well below the peak of the CMB. Similar radiation at early times may also
contribute a fraction of the GHz range excess observed by ARCADE2.
