Strong-coupling behavior of φ4 theories and critical exponents

We use the recently developed variational perturbation theory to continue the renormalization constants of three-dimensional phi(4) theories to the regime of strong bare coupling g(0). In this limit, they are found to behave as powers in go, thereby determining all critical exponents. Convergent strong-coupling expansions are found for all renormalization group functions which converge well even in the weak-coupling limit. [S0556-2821(98)04502-0].