DERIVATIVE EXPANSION OF THE RENORMALIZATION-GROUP IN O(N) SCALAR FIELD-THEORY

We apply a derivative expansion to the Legendre effective action flow equations of O(N) symmetric scalar field theory, making no other appro ximation. We calculate the critical exponents eta, nu, and omega at th e both the leading and second order of the expansion, associated to th e three-dimensional Wilson-Fisher fixed points, at various values of N . In addition, we show how the derivative expansion reproduces exactly known results, at the special values N = infinity, -2, -4,... (C) 199 8 Elsevier Science B.V.