Abstract

In this paper we show the Wilson effective action for the 2-dimensional O(N + 1)-symmetric lattice nonlinear sigma-model computed in the 1-loop approximation for the nonlinear choice of blockspin Phi(x), Phi(x) = C phi(x)/-C phi(x)-,where C is averaging of the fundamental field phi(x) over a square x of side (a) over tilde. The result for S-eff is composed of the classical perfect action with a renormalized coupling constant beta(eff), an augmented contribution from a Jacobian, and further genuine 1-loop correction terms. Our result extends Polyakov's calculation which had furnished those contributions to the effective action which are of order ln (a) over tilde/a, where a is the lattice spacing of the fundamental lattice. An analytic approximation for the background field which enters the classical perfect action will be presented elsewhere [1].