A MODE-COUPLING ANALYSIS OF THE CENTRAL PEAK AT ORDER-DISORDER PHASE-TRANSITIONS

The influence of local and translation invariant memory effects on the critical dynamics of a model undergoing a continous structural phase transition from a disordered (T > T(c)) to an ordered distorted phase (T < T(c)) is studied by mode coupling theory above the critical tempe rature T(c). It is shown that besides the existence of critical slowin g-down modes there also exists a central peak as a consequence of corr elations of the critical modes, increasing with the critical exponent gamma when approaching T(c). The dependence of the central peak on the wavevector q over arrow pointing right, temperature T and on the spat ial dimension d is investigated. For d = 3 a scenario with local long time memory correlations is compared with respect to its temperature a nd momentum dependence with a model using translation invariant long t ime memory correlations.