Critical Behavior of the Anisotropicn-Vector Model

The critical behavior of a system of n-component classical "spins"with anisotropic pair interactions is discussed using renormalization-group techniques for dimension d=4-. To first order in the correlation and susceptibility exponents in the isotropic limit are 2==1+ (n+2) 2 (n+8), while the anisotropy or crossover exponent is =1+n2 (n+8). When n these expansions agree with exact spherical-model results. For n=3 and d=3 series expansions indicate 1. 2 (compared with 1. 38).