J. L. Sobrinho, P. Augusto, A. L. Gonçalves
Primordial black holes (PBHs) might have formed in the early Universe as a consequence of the collapse of density fluctuations with an amplitude above a critical value δc: the formation threshold. Although for a radiation-dominated Universe delta(c) remains constant, if the Universe experiences some dust-like phases (e.g. phase transitions) δc might decrease, improving the chances of PBH formation. We studied the evolution of δc during the quantum chromodynamics (QCD) phase transition epoch within three different models: bag model (BM), lattice fit model, and crossover model. We found that the reduction on the background value of δc can be as high as 77 per cent (BM), which might imply a ~10-10 probability of PBHs forming at the QCD epoch.
black hole physics, early Universe, inflation
Monthly Notices of the Royal Astronomical Society
Volume 463, Issue 3, Page 2348