Abstract
Quantum effects on the static critical behaviour of an isotropic n-vector model undergoing a displacement-type phase transition are studied at Tc and to O(1/n). For Tc not=0 there is no quantum effect on eta , and for Tc=0 one gets eta =0 for d>3, and for 2<d<3 eta is due to quantum fluctuations, implying that it assumes a different value than in the classical case. The dynamical behaviour of the system violates the dynamic scaling hypothesis.