Stiff-Glass Approximation of Mode-Coupling Theory

The stiff-glass approximation of the mode-coupling theory of the glass-transition–as introduced in a recent paper by G"otze 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 neglection of two-phonon processes and thus provides a clear physical picture for the MCT solutions deep in the glass. In addition, the effect of additional symplifying approximations and the combination of these approximations is studied.