The long and short of random media: Acoustic Anderson localization Free

Wave propagation in random media relates to a large number of important current problems in physics and acoustics. For long wavelengths the wave equation is locally approximated by the Laplace equation, and this together with the complex boundary conditions provided by the random medium describes many interesting phenomena involving percolation, fractional dimensionality, etc. An important puzzle in the long wavelength regime was solved just recently; a homework problem once assigned by I. Rudnick provided the key to the solution. In the short wavelength regime, where wavelengths are on the order of the variations in the random medium, one may observe effects of Anderson localization, which is currently receiving much attention in the study of quantum phenomena in disordered solids. Recent experiments on acoustic Anderson localization, including nonlinear effects, will be reported. [Work supported by ONR.]