Black hole atom as a dark matter particle candidate
  We propose the new dark matter particle candidate - the "black hole atom",
which is an atom with the charged black hole as an atomic nucleus and electrons
in the bound internal quantum states. As a simplified model we consider the the
central Reissner-Nordstrom black hole with the electric charge neutralized by
the internal electrons in bound quantum states. For the external observers
these objects would look like the electrically neutral Schwarzschild black
holes. We suppose the prolific production of black hole atoms under specific
conditions in the early universe.
