MORE ON THE SIGMA TO FERMION MASS-RATIO IN THE LINEAR SIGMA-MODEL ANDNAMBU-JONA-LASINIO MODEL

We calculate the two-loop contributions to the beta functions for the Yukawa coupling constant G and the four-scalar coupling constant lambd a in the linear sigma model using a mass-independent renormalization s cheme. The results are used to obtain a correction to the infrared fix ed point value for lambda/G2. We argue that this is the leading correc tion to the fixed point value for this ratio in the regime of fine-tun ing, and use our results to complete a calculation of the ratio of the sigma mass to the fermion mass to order G2 . Our calculation also app lies to the Nambu-Jona-Lasinio model.