Multi-quark interactions with a globally stable vacuum

It is shown that U(3)(L) x U(3)(R) eight-quark interactions stabilize the asymmetric ground state of the well-known model with four-quark Nambu-Jona-Lasinio and six-quark 't Hooft interactions. The result remains when the reduced SU(3) flavour symmetry is explicitly broken by the general current quark mass term with (m) over cap (u) not equal (m) over cap (d) not equal (m) over cap (s). (c) 2006 Elsevier B.V. All rights reserved.