Primordial black holes in braneworld cosmologies: Accretion after formation

We recently studied the formation and evaporation of primordial black holes in a simple braneworld cosmology, namely Randall-Sundrum Type II. Here we study the effect of accretion from the cosmological background onto the black holes after formation. While it is generally believed that in the standard cosmology such accretion is of negligible importance, we find that during the high-energy regime of braneworld cosmology accretion can be the dominant effect and lead to a mass increase of potentially orders of magnitude. However, unfortunately the growth is exponentially sensitive to the accretion efficiency, which cannot be determined accurately. Since accretion becomes unimportant once the high-energy regime is over, it does not affect any constraints expressed at the time of black hole evaporation, but it can change the interpretation of those constraints in terms of early Universe formation rates.Comment: 6 pages RevTeX4 file. Extension to discussion of thermal balance and grey-body factor