Field work and dispersion relations of excitations on fractals

Abstract
An approach to finding the dispersion law of excitations on fractals for an arbitrary interaction is developed. It is based on the scale invariance of the probe-field work and allows one to express exponents of the dispersion law in terms of the spectral and Hausdorff dimensions. The expressions obtained for the dispersion-law exponent are different for vibrational (Goldstone-type) and dipolar (non-Goldstone-type) excitations, in agreement with previous results of Alexander and Orbach and those of the authors of the present paper.