Primordial black hole dark matter in dilaton-extended two-field
  Starobinsky inflation
  We investigate the production of primordial black holes and their
contribution to the presently observed dark matter in a dilaton two-field
extension of Starobinsky's quadratic $f(R)$ model of inflation. The model
features a multi-field amplification mechanism which leads to the generation of
a sharp peak in the inflationary power spectrum at small wavelengths
responsible for the production of primordial black holes. This mechanism is
significantly different from single-field models and requires a stochastic
treatment during an intermediate phase of the inflationary dynamics. We find
that the model leads to a successful phase of effective single-field
Starobinsky inflation for wavelengths probed by the cosmic microwave background
radiation and explains the observed cold dark matter content in the Universe by
the formation of primordial black holes.
