Monopole order parameter in SU(2) lattice gauge theory

We report the results of numerical calculations for the probability distribution of the values of the monopole creation operator Ф_mon in the maximal Abelian projection of SU(2) lattice gluodynamics. It turns out that at low temperature in the confinement phase the maximum of the distribution corresponds to a nonzero value of the field Ф_mon. This means that the effective potential has the form of a Higgs potential. Above the phase-transition point the minimum of the potential (the maximum of the distribution of the monopole creation operator) corresponds to a zero value of the monopole field Fmon. The results presented are a direct proof of the existence of a condensate of Abelian monopoles in the confinement phase of gluodynamics, and they confirm the hypothesis that the vacuum of gluodynamics is analogous to a dual superconductor. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 6, 392–397 (25 March 1996)