Stiff-glass approximation of mode-coupling theory

The stiff-glass approximation of the mode-coupling theory of the glass-transition (MCT) - as introduced in a recent paper by Gotze and Mayr for a discussion of phenomena resembling the Boson peak and high-frequency sound observations made in real glass-formers - is examined in detail. It amounts to a neglect of the two-phonon processes and thus provides a clear physical picture for the MCT solutions deep in the glass. In addition, the effect of additional simplifying approximations and the combination of these approximations is studied. (C) 2002 Elsevier Science B.V. All rights reserved.