DISCONNECTION TRANSITION IN AN EXTENDED DELTA-FUNCTION BOSE-GAS

A disconnection transition is a phase transition which accompanies a c hange in the connectedness of the fermi sea. The existence of such a t ransition is established in the context of a one-dimensional interacti ng model. The model considered is an extension of the delta function b ose gas in which its fourth order conservation law is added to the ori ginal hamiltonian. For low density, the ground state of the model cons ists of two separated fermi seas and there are two distinct branches o f excitations. At a critical density, one branch of excitations disapp ears, and there is a second order phase transition to a single fermi s ea ground state.