Spontaneously broken ground states of the U(n)L x U(n)R linear sigma model at large n

Symmetry breaking patterns of the U(n)(L) x U(n)(R) symmetric meson model are investigated in a formulation involving three auxiliary composite fields. The effective potential is constructed at leading order in the 1/n expansion for a condensate belonging to the center of the U(n) group. A wide region is found in the coupling space, where, in addition to the condensate proportional to the unit matrix, also metastable minima exist even in the chiral limit, in which a further breakdown of the diagonal U-V(n) symmetry to U-V(n - 1) is realized. Application of a moderate external field conjugate to this component of the order parameter changes this state into the true ground state of the system.