Diquark bosonisation of the Nambu model

A U(1)xU(1) chirally symmetric version of the Nambu-Jona-Lasinio model with scalar and vector interactions, is rewritten in diquark and meson variables. Integration over the quark fields yields the (bosonised) effective action for diquarks and mesons. For small values of the vector coupling, the bosonised action exhibits spontaneous breaking of chiral symmetry. For sufficiently large values of the vector coupling, however, a diquark condensate forms instead, and colour symmetry is spontaneously broken. (orig.)