Superheavy dark matter in $R^2$-cosmology
  The conventional Friedmann cosmology is known to be in tension with the
existence of stable particles having interaction strength typical for
supersymmetry and heavier than several TeV. A possible way to save life of such
particles may be a modification of the standard cosmological expansion law in
such a way that the density of these heavy relics would be significantly
reduced. We study particle creation in the Starobinsky inflationary model for
different decay channels of the scalaron. It is shown that in the process of
thermalization superheavy stable particles with the coupling strength typical
for the GUT SUSY could be created with the density equal to the observed
density of dark matter.
