Primordial black hole formation during the QCD phase transition: threshold, mass distribution and abundance

Understand

Primordial black hole (PBH) formation during cosmic phase transitions and annihilation periods, such as the QCD transition or the $e^+e^-$-annihilation, is thought to be particularly efficient due to a softening of the equation of state.

• We present a detailed numerical study of PBH formation during the QCD epoch in order to derive an accurate PBH mass function.
• We also briefly consider PBH formation during the $e^+e^-$-annihilation epoch.
• Our investigation confirms that, for nearly scale-invariant spectra, PBH abundances on the QCD scale are enhanced by a factor $\sim 10^3$ compared to a purely radiation dominated Universe.