ON THE APPLICABILITY OF MODE-COUPLING THEORY TO A PHI(4)-MODEL WITH FIRST-ORDER PHASE-TRANSITION

A phi(4)-model with symmetric double-well-like on-site potential and a nharmonic, infinite range interactions is investigated. This model exh ibits a first order phase transition at a temperature T-c. The time-de pendent displacement correlation function is studied in the framework of the mode coupling theory (MCT). Depending on the choice of slow mod es, MCT makes qualitatively different predictions which are compared w ith MD-results. These numerical results suggest that only the order pa rameter mode (x) over tilde(q = 0), should be considered as slow. In t hat case it is shown that MCT yields a dynamical transition in the sup ercooled high-temperature phase ([<(x)over tilde (q = 0)>] = 0) at a t emperature T which coincides with the spinodal temperature T-s (T-s = 0 for our model) where the metastable supercooled phase becomes insta ble.