Primordial Black Holes from Passive Density Fluctuations
  In this paper, we show that if passive fluctuations are considered,
primordial black holes (PBHs) can be easily produced in the framework of
single-field, slow-roll inflation models. The formation of PBHs is due to the
blue spectrum of passive fluctuations and an enhancement of the spectral range
which exits horizon near the end of inflation. Therefore the PBHs are light
with masses $\lesssim 10^{15}g$ depending on the number of e-folds when the
scale of our observable universe leaves horizon. These PBHs are likely to have
evaporated and cannot be a candidate for dark matter but they may still affect
the early universe.
