PI-MESON AND A(1)-MESON PHYSICS IN CURRENT-ALGEBRA AT THE QUARK LEVEL

The a(1)-->pi(pi pi) S-wave decay and the low-energy pi pi-scattering are considered within current algebra at the quark level (CA)(q) and c hiral perturbation theory at the quark level (CHPT)(q) based on the ex tended Nambu-Jona-Lasinio model with linear realization of chiral U(3) x U(3) symmetry. It is shown that low-energy interactions of a new ki nd, produced by convergent constituent-quark diagrams and being very u seful for the theoretical understanding of experimental data on the pr ocesses under consideration, are very good blending with (CA)(q) and ( CHPT)(q). The contribution of these interactions is caused by the appl ication of ordinary rules of quantum field theory. These interactions allow one to escape the problem of the quark condensate, vanishing in the chiral limit.