Brillouin scattering on porous silica aerogels reveals the onset of the phonon-to-fracton crossover in both the wave-vector and density dependence of the spectra. The results are consistent with a fractal description, giving both the fractal dimension D and the spectral dimension d ̃ \~{}{}. In the hypothesis that the samples form single infinite clusters, the numerical values suggest that scalar elasticity is significant in these materials.
No takes yet. Share an insight, caveat, or question.
Courtens et al. (1987) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: