Evaporating primordial black holes as varying dark energy
  If light enough primordial black holes (PBH) account for dark matter, then
its density decreases with time as they lose mass via Hawking radiation. We
show that this time-dependence of the matter density can be formulated as an
equivalent $w(z)$ dark energy model and we study its implications on the
expansion history. Using our approach and comparing with the latest
cosmological data, including the supernovae type Ia, Baryon Acoustic
Oscillations, Cosmic Microwave Background and the Hubble expansion H(z) data,
we place observational constraints on the PBH model. We find that it is
statistically consistent with $\Lambda$CDM according to the AIC statistical
tool. Furthermore, we entertain the idea of having a population of ultra-light
PBHs, decaying around neutrino decoupling, on top of the dark matter fluid and
show how this offers a natural dark matter-radiation coupling altering the
expansion history of the Universe and alleviating the $H_0$ tension.
