Primordial black holes from an electroweak phase transition
  We propose a mechanism that forms primordial black holes (PBHs) via a
first-order electroweak phase transition (FOEWPT). The FOEWPT is realized by
extending the Standard Model with a real singlet scalar, while the PBH
formation is achieved by the collapse of non-topological solitons called
Fermi-balls. Such solitons form via trapping fermions in the false vacuum
during the FOEWPT, and they eventually collapse into PBHs due to the internal
Yukawa attractive force. We demonstrate that a scenario with PBH dark matter
candidate can exist, and the typical experimental signals include FOEWPT
gravitational waves and the multi-lepton/jet or displaced vertex final states
at the LHC.
