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The effective potential of the confinement order parameter in the Hamiltonian Approach

The effective potential of the order parameter for confinement is calculated within the variational approach to the Hamilton formulation of Yang-Mills theory. Compactifying one spatial dimension and using a background gauge fixing this potential is obtained by minimizing the energy density for a given constant and color diagonal background field directed along the compactified dimension. Using Gaussian type trial wave functionals I establish an analytic relation between the propagators in the background gauge at finite temperature and the corresponding zero temperature propagators in Coulomb gauge. In the simplest truncation, neglecting the ghost and using the ultraviolet form of the gluon energy one recovers the Weiss potential. On the other hand from the infrared form of the gluon energy one finds an effective potential which yields a vanishing Polyakov loop indicating the confined phase. From the full non-perturbative potential (with the ghost included) one extracts a critical temperature of the deconfinement phase transition of 269 MeV for the gauge group SU(2) and 283 MeV for SU(3).