A new approach to the determination of the critical couplings for a deconfinement phase transition in the variational-cumulant expansion

Based on the variational-cumulant expansion (VCE), a new approach is adopted to determine the critical couplings for the deconfinement phase transition in SU(2) gauge theory for N_τ = 2, 3, 4, and with both the standard Wilson action and the improved tree-level Symansik action. New results of the VCE which are close to the data of Monte Carlo (MC) simulations make manifest that the new approach is much more effective than the traditional one and show the consistence of a VCE analysis with an MC simulation.