A linear SU(n) u model with spin-zero mesons is demonstrated to be renormalizable in the one-loop approximation for n 2 4. The mesons are assigned to the ( n , n *) @ ( n *, n ) representation of SU(n) X SU(n).The model incorporates both Nambu-Goldstone symmetry breaking and explicit symmetry-breaking terms linear in the fields. The counterterms are evaluated. As an additional four-point coupling is available in the SU(4) case, the SU(4) model is considered separately. A number of useful relations among the SU(n) f and d tensors are presented.

We unitarize the low-energy symmetric aN amplitude introduced by Altarelli et a l . under the assumption that the 2n intermediate state in the t-channel unitarity condition i s the dominant contribution. The low-energy nn amplitude i s described using a model of Graham and Johnson. The unitarity corrections at the current-algebra point a r e found to be small. Hence, considerations of t-channel analyticity probably do not seriously affect the calculation by Cheng and Dashen of the ~T N o term.