Strong coupling series of string tension and mass gap in lattice gauge theory

We have calculated the strong coupling expansion series for the string tension and mass gap in three-dimensional Z2 lattice gauge theory using finite-lattice method. The expansion is equivalent to the low temperature expansion of the surface tension and inverse correlation length in D = 3 Ising model. We have obtained the series to order β34 for the string tension and β30 for the mass gap, which are about two times longer than those obtained by the standard graphical method. (orig.)