Founding theoretical paper proposing that a first-order QCD quark-hadron phase transition in the early universe could concentrate the cosmic quark excess into dense, invisible “quark nuggets,” and that strange quark matter (roughly equal u,d,s quarks) could be the true ground state of baryonic matter if its energy per baryon is below 938 MeV — the theoretical possibility underlying “strangelets.” relevance_note: root theoretical claim that stable strange quark matter could exist and convert ordinary matter, the premise the strangelet-doomsday scenario needs.