Magnetic monopoles from gauge theory phase transitions

Thermal fluctuations of the gauge field lead to monopole formation at the grand unified phase transition in the early universe, even if the transition is merely a smooth crossover. The dependence of the produced monopole density on various parameters is qualitatively different from theories with global symmetries, and the monopoles have a positive correlation at short distances. The number density of monopoles may be suppressed if the grand unified symmetry is only restored for a short time by, for instance, non-thermal symmetry restoration after preheating