Primordial Black Holes as Seeds of Supermassive Black Holes: A Feasibility Calculation

Black holes of a billion solar masses are observed powering quasars less than a billion years after the Big Bang. Growing them from stellar remnants by Eddington-limited accretion is arithmetically uncomfortable: the exponential growth clock, set by the Salpeter time, allows only a limited number of e-folds before the observed epoch, and the required starting mass climbs steeply as the duty cycle or the radiative efficiency worsens. The headline computed values are: seed duty1 = 1.90e+01; seed duty05 = 1.38e+05. The study is a computation from stated assumptions, not a measurement, and the deposited script reproduces every number quoted.