Universal Sound Attenuation in Amorphous Solids

A large class of amorphous materials, including glasses, polymers, disordered crystals and in some cases quasi-crystals and proteins, show a striking degree of universality in their low temperature acoustic and thermal properties. Among the least understood is the dimensionless acoustic mean path $l/\lambda \sim 150$. Although many theories have been proposed to explain the universality of this constant, they rely on detailed phenomenological assumptions, such as the existence of tunneling two-state systems. In this talk, I present the many-body acoustic response of elastically coupled random matrices to demonstrate that the universality is a property of a general class of theories, and emerges regardless of the detailed assumptions regarding the constituents of the amorphous solid.