Cosmic microwave background bounds on primordial black holes.
(based on arXiv:2002.10771 and arXiv:1707.04206)
After briefly reviewing the effects through which primordial black holes (PBH) affect the cosmic microwave background (CMB), I will focus on the impact that accreting, heavy PBH (stellar mass or heavier) have on CMB anisotropies. The key aspects of the accretion process in a cosmological setting are then illustrated. If PBH do not constitute the totality of the dark matter, it is important to take into account the effect of the dark matter halo growing around PBH in catalysing the baryonic matter accretion. I will present the bounds from an analysis on current cosmological data and discuss their implication on a primordial origin for the supermassive black holes observed at high redshift.