Abstract
The fast-dynamics spectrum in glasses is analysed using a model which ascribes the quasielastic contributions to scattering of photons or neutrons by the vibrations around the boson peak. It is shown that the model describes well the results of neutron and light scattering measurements and explains many peculiar properties of the broad quasielastic spectra. The analysis presented demonstrates that this ‘indirect’ mechanism of quasielastic scattering, which is neglected in many models, can be the most significant for glass-forming systems.