Linked cluster expansions for U(1) lattice gauge theory in 2+1 and 3+1 dimensions

Compact U(1) lattice gauge theory is studied in 2+1 and 3+1 dimensions using strong coupling series expansions and the recently proposed exact linked cluster expansion algorithm. Results for the vacuum energy, specific heat and axial string tension in 2+1 dimensions are in agreement with previous finite lattice estimates. In 3+1 dimensions, we present new strong coupling series results (order g-40) which together with the ELCE estimates show evidence of a continuous phase transition at x=1/g4=0.72+-0.08. The associated critical index for the vanishing string tension is μ=0.65+-0.12. The axial string tension in D=3+1 appears to undergo a non-deconfining roughening transition at smaller x(0.56+-0.07). (orig.)