MRI Driven Black Holes as Dark Matter

We demonstrate via long duration general relativistic magnetohydrodynamic (GRMHD) simulations that MRI-dominatedaccretion at least hundreds of gravitational radii from black holes can occur under conditions expected in the Positronium Era. We thereby identify that the positronium plasma that existed 0.01 s to 14 s into the Big Bang can serve as the primary source of mass that augmented primordial blackhole seeds to $10^{16-17}$g black holes contributing to dark matter today. This population of black holes, in turn, radiates in a manner consistent with the observed gamma ray background. At a time of uncertainty about the role of new kinds of particles, the better understood primordial black hole MRI accretion process may be the best way to pin down how much %and whether dark matter mass lies behind horizons versus new dark sector particles.