New thresholds for Primordial Black Hole formation during the QCD phase transition

Understand

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 $\delta_{c}$: 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) $\delta_{c}$ might decrease, improving the chances of PBH formation.
• We studied the evolution of $\delta_{c}$ during the QCD phase transition epoch within three different models: Bag Model (BM), Lattice Fit Model (LFM), and Crossover Model (CM).