Résumé
The magnetic monopole of a dark sector has been advocated as an appealing dark matter candidate. We revisit the computation of the monopole abundance$Ω_M$ , generated by a thermal phase transition in the minimal 't Hooft-Polyakov model. We explore the three regimes where the phase transition is second order, weakly first order, or supercooled, identifying the parameter space regions where$Ω_M$can match the observed dark matter abundance. However, the dark sector necessarily contains a stable electrically-charged particle, namely a massive vector boson, with a calculable abundance$Ω_{W'}$ . We show that, under minimal assumptions,$Ω_{W'}$is always far larger than$Ω_M$ : dark monopoles cannot constitute a sizeable fraction of dark matter.