Hadron physics and primordial black holes

The implications for hadron physics of astrophysical observations relating to primordial black holes are discussed. If one assumes that fluctuations in the space-time metric at very early times were scale invariant then the speed of sound in the primordial fireball must exceed $0.01c$ at times earlier than 10^-12 sec, as a consequence of observational limits on primordial black holes. This suggests that superbaryons probably do not exist. It is further shown that black holes with masses 10²⁵ g are unlikely to exist in nature unless either the spectrum of density fluctuations or the equation of state of dense hadronic matter behave in a rather special way.