Key points are not available for this paper at this time.
Primordial black holes (PBHs) may be part of the dark matter. It is shown here that PBHs form more easily during cosmic phase transitions. For approximately scale-invariant primordial curvature fluctuations the PBH mass function may therefore leave a record of the thermal history of the early Universe. In particular a peak is expected on the 1.9 solar mass scale due to the cosmic QCD transition.
Karsten Jedamzik (Wed,) studied this question.