$\delta$ expansion applied to strong-coupling Z(2), U(1), and SU(2) gauge theory on the lattice in four dimensions

We generalize to four dimensions the linear $\delta$ expansion applied to gauge theory on the lattice, with Z(2), U(1), and SU(2) as the gauge groups and an unperturbed action appropriate to the strong-coupling regime. The calculation is carried to fourth order in $\delta$, using the machinery of character expansions. The expansion is optimized in a bid to improve upon existing strong-coupling methods and our results are compared against results from these and from Monte Carlo calculations.