On Primordial Black Holes generated from inflation with solo/multi-bumpy
  potential
  It is well known that primordial black hole (PBH) can be generated in
inflation process of the early universe, especially when the inflaton field has
some non-trivial features that could break the slow-roll condition. In this
paper, we investigate a toy model of inflation with bumpy potential, which has
one or several bumps. We found that potential with multi-bump can give rise to
power spectra with multi-peaks in small-scale region, which can in turn predict
the generation of primordial black holes in various mass ranges. We also
consider the two possibilities of PBH formation by spherical collapse and
elliptical collapse.
