Evolution of primordial black holes in a dissipative FLRW universe
  This paper deals with the study of the evolution of PBHs in an FLRW universe
with dissipation due to bulk viscosity which is considered to be in the form of
isentropic gravitational particle creation. Assuming that the process of
evaporation is quite suppressed during the early radiation era, we obtain an
analytic solution for the evolution of PBH mass by accretion during this era,
subject to an initial condition. We also obtain an upper bound on the accretion
efficiency $\epsilon$ for $a \sim a_r$, where $a_r$ is the point of transition
from the early de Sitter to the radiation era. Furthermore, aided by Maple 13,
we obtain numerical solutions for the mass of a hypothetical PBH with intial
mass 100 g assumed to be formed at an epoch when the value of the Hubble
parameter was, say, 1 km/s/Mpc. We consider three values of the accretion
efficiency, $\epsilon=0.23,0.5$, and $0.89$ for our study. The analysis reveals
that the mass of the PBH increases rapidly due to the accretion of radiation in
the early stages of its evolution. The accretion continues but its rate
decreases gradually with the evolution of the Universe. Finally, Hawking
radiation comes into play and the rate of evaporation surpasses the rate of
accretion so that the PBH mass starts to decrease. As the Universe grows,
evaporation becomes the dominant phenomenon, and the mass of the PBH decreases
at a faster rate.
