  We analyze wave propagation in the vacuum of Podolsky regularized
electrodynamics. Two kinds of waves were found in the theory: the traditional
non-dispersive waves of Maxwell electrodynamics, and a dispersive wave
reminiscent of wave propagation in a collisionless plasma. Charged particle
concentration was determined, and found to be huge in this vacuum. We interpret
the results in terms of vacuum polarization effects induced in an otherwise
classical theory.
