Asymptotic primordial-black-hole mass after radiation accretion

Determine the finite asymptotic mass approached by the primordial black hole formed from an over-the-barrier Higgs-like fluctuation as accretion from the surrounding radiation background becomes progressively less efficient at late cosmological times.

Background

In both the subcritical and supercritical branches, the parent radiation-dominated universe is left with an ordinary primordial black hole. The simulations follow continued apparent-horizon growth consistent with accretion from the surrounding radiation fluid.

Because the radiation density redshifts, the authors expect accretion eventually to become inefficient and the black-hole mass to approach a finite asymptotic value. The simulated time interval is insufficient to calculate that limiting mass quantitatively, leaving its determination unresolved.