A simple random matrix model for the vibrational spectrum of jammed packings

To better understand the surprising low-frequency vibrational modes in structural glasses, we study the spectra of a large ensemble of sparse random matrices where disorder is controlled by the distribution of bond weights and network coordination. We find D(ω) has three regimes: a very-low-frequency regime that can be predicted analytically using extremal statistics, an intermediate regime with quasi-localized modes, and a plateau with D(ω) ∼ω^0. In the special case of uniform bond weights, the intermediate regime displays D(ω) ∼ω^4, independent of network coordination and system size, just as recently discovered in simulations of structural glasses.