Super-horizon primordial black holes: How do they grow?

Primordial black holes have important observational implications through Hawking evaporation and gravitational radiation as well as being a candidate for cold dark matter. Those black holes may have formed in the early universe typically with the mass scale contained within the Hubble horizon at the formation epoch and subsequently accreted the mass surrounding them. Numerical relativity simulation shows that primordial black holes of different masses do not accrete much, which contrasts with a simplistic Newtonian argument. Primordial black holes larger than the cosmological horizon have non-standard global structure, suggesting that they may have formed in inflationary cosmology.