title: Dynamical structure factor in disordered systems
abstract: We study the spectral width as a function of the external momentum for the dynamical structure factor of a disordered harmonic solid, considered as a toy model for supercooled liquids and glasses. In the contexts of both the single-link coherent potential approximation and a single-defect approximation, two different regimes are clearly identified: if the density of states at zero energy is zero, the usual p(4) law is recovered for small momentum. On the contrary, if the disorder induces a nonvanishing density of states at zero energy, a linear behavior is obtained. The dynamical structure factor is numerically calculated in lattices as large as 96(3) and satisfactorily agrees with the analytical computations.
authors.affiliation: Dipartimento di Fisica, Universita di Roma "La Sapienza," INFN Sezione di Roma - INFM Unita di Roma, Piazzale Aldo Moro 2, 00185 Roma, Italy.
authors.initials: V
authors.lastname: Martin-Mayor
authors.initials: G
authors.lastname: Parisi
authors.initials: P
authors.lastname: Verrocchio