  Massive Primordial Black Holes (MPBH) can be formed after inflation due to
broad peaks in the primordial curvature power spectrum that collapse
gravitationally during the radiation era, to form clusters of black holes that
merge and increase in mass after recombination, generating today a broad
mass-spectrum of black holes with masses ranging from 0.01 to $10^5~M_\odot$.
These MPBH could act as seeds for galaxies and quick-start structure formation,
initiating reionization, forming galaxies at redshift $z>10$ and clusters at
$z>1$. They may also be the seeds on which SMBH and IMBH form, by accreting gas
onto them and forming the centers of galaxies and quasars at high redshift.
They form at rest with zero spin and have negligible cross-section with
ordinary matter. If there are enough of these MPBH, they could constitute the
bulk of the Dark Matter today. Such PBH could be responsible for the observed
fluctuations in the CIB and X-ray backgrounds. MPBH could be directly detected
by the gravitational waves emitted when they merge to form more massive black
holes, as recently reported by LIGO. Their continuous merging since
recombination could have generated a stochastic background of gravitational
waves that could eventually be detected by LISA and PTA. MPBH may actually be
responsible for the unidentified point sources seen by Fermi, Magic and
Chandra. Furthermore, the ejection of stars from shallow potential wells like
those of Dwarf Spheroidals (DSph), via the gravitational slingshot effect,
could be due to MPBH, thus alleviating the substructure and too-big-to-fail
problems of standard collisionless CDM. Their mass distribution peaks at a few
tens of $M_\odot$ today, and could be detected also with long-duration
microlensing events, as well as by the anomalous motion of stars in GAIA. Their
presence as CDM in the Universe could be seen in the time-dilation of lensed
images of quasars.
