Ultraviolet divergences in1Nexpansions of asymptotically free theories

Abstract
We calculate the ultraviolet divergences of the nonlinear σ and Gross-Neveu models in the 1N expansion near two dimensions (d=2ε). Beyond the leading order the theories develop logarithmic as well as pole singularities in ε. Identical divergences occur when the renormalization constants calculated in perturbation theory are expanded in powers of 1N rather than in powers of the coupling constants. The necessary infinite renormalizations of the 1N expansions are completely determined by the two-loop β functions and one-loop anomalous dimensions of perturbation theory. These results can be extended to non-Abelian gauge theories in four dimensions which admit 1N expansions.