Probing quantum gravity using high-energy astrophysics
  The events observed by LIGO indicate the existence of a large population of
intermediate mass black holes. This unexpected result lead to a resurgence in
the interest in theories of the formation of primordial black holes with
several studies showing that broad mass distributions can evade or satisfy the
stringent constraints on monochromatic populations. If such large populations
exist they provide the perfect test-bed for theories beyond the standard model
of physics that modify black hole evolution. The case we studied is that of
"Planck stars", a hypothetical modification of the black hole evolution where
it explodes via quantum loop gravity motivated tunnelling. We determine what
the high-frequency background signal of such objects exploding over the whole
of cosmic history would look like for various black hole populations to place
actual empirical constraints on quantum loop gravity via comparison to observed
isotropic background signals at the same frequencies. We find that stringent
constraints heavily restrict the amount of energy released via the high-energy
channel, thereby casting doubt on whether or not the high-energy signal could
result in gamma-ray bursts as speculated in the literature.
