Some Generic Aspects of Bosonic Excitations in Disordered Systems
Some Generic Aspects of Bosonic Excitations in Disordered Systems
We consider noninteracting bosonic excitations in disordered systems, emphasizing generic features of quadratic Hamiltonians in the absence of Goldstone modes. We discuss relationships between such Hamiltonians and the symmetry classes established for fermionic systems. We examine the density $\ensuremath{\rho}(\ensuremath{\omega})$ of excitation frequencies $\ensuremath{\omega}$, showing how the universal behavior $\ensuremath{\rho}(\ensuremath{\omega})\ensuremath{\sim}{\ensuremath{\omega}}^{4}$ for …