Holographic principle bounds on primordial black-hole abundances

The generalized second law of thermodynamics and the holographic principle are combined to obtain the maximum mass of black holes formed inside a static spherical box of size R filled with radiation at initial temperature Ti. The final temperature after the formation of black holes is evaluated, and we show that a critical threshold exists for the radiation to be fully consumed by the process. We next argue that if some form of holographic principle holds, upper bounds to the mass density of PBHs formed in the early universe may be obtained. The limits are worked out for inflationary and non-inflationary cosmological models. This method is independent of the known limits based on the background fluxes (from cosmic rays, radiation and other forms of energy) and applies to potentially important epochs of PBH formation, resulting in quite strong constraints on (OMEGA)pbh.