Hawking-Radiation Recoil of Microscopic Black Holes
  Hawking radiation would make microscopic black holes evaporate rapidly, which
excludes them from many astrophysical considerations. However, it has been
argued that the quantum nature of space would alter this behaviour: the
temperature of a Planck-size black hole vanishes, and what is left behind is a
Planck-mass remnant with the cross-section of $\approx 10^{-70}\mbox{m}^2$,
which makes a direct observation nearly impossible. Such black hole remnants
have been identified as possible dark matter candidates. Here, we argue that
the final stage of evaporation has a recoil effect that gives them a velocity
up to $\approx 10^{-1} c$. This would lead to a disagreement with the cold dark
matter cosmological model unless the primordial black hole formation ceased
shortly after the inflation era.
