Direct detection of primordial black hole relics as dark matter
  If dark matter is composed of primordial black holes, such black holes can
span an enormous range of masses. A variety of observational constraints exist
on massive black holes, and black holes with masses below $10^{15}\,\mathrm{g}$
are often assumed to have completely evaporated by the present day. But if the
evaporation process halts at the Planck scale, it would leave behind a stable
relic, and such objects could constitute the entirety of dark matter. Neutral
Planck-scale relics are effectively invisible to both astrophysical and direct
detection searches. However, we argue that such relics may typically carry
electric charge, making them visible to terrestrial detectors. We evaluate
constraints and detection prospects in detail, and show that if not already
ruled out by monopole searches, this scenario can be largely explored within
the next decade using existing or planned experimental equipment. A single
detection would have enormous implications for cosmology, black hole physics,
and quantum gravity.
