Cosmological production of black holes

It is argued that, at a first-order phase transition, false-vacuum bubbles may occasionally collapse to become black holes. If the critical temperature ${\mathit{T}}_{\mathit{c}}$ is less than a TeV, these black holes, which have a mass proportional to ${\mathit{M}}_{\mathrm{Pl}}^2$/${\mathit{T}}_{\mathit{c}}$, could survive until today to be the dark matter. Alternatively, evaporation of black holes could give rise to relic particle abundances.