Transport in the random Kronig-Penney model
  The Kronig-Penney model with random Dirac potentials on the lattice $\ZM$ has critical energies at which the Lyapunov exponent vanishes and the density of states has a van Hove singularity. This leads to a non-trivial quantum diffusion even though the spectrum is known to be pure-point. 
Maxim Drabkin, Werner Kirsch, Hermann Schulz-Baldes
math-ph math.MP