  There has been renewed interest in the physics of the so-called crossover for
current fluctuations in mesoscopic conductors, most recently involving the
possibility of its appearance in the passage to the macroscopic limit. Shot
noise is normally absent from solid-state conductors in the large, and its
anomalous resurgence there has been ascribed to a rich interplay of drift,
diffusion, and Coulomb screening. We demonstrate that essentially the same rise
in shot noise occurs in a much less complex system: the Boltzmann-Drude-Lorentz
model of a macroscopic, uniform gas of strictly noninteracting carriers. We
conclude that the "anomalous crossover" is a manifestation of simple kinetics.
Poissonian carriers, if driven by a high enough field, cross the sample faster
than any scattering time, thus fulfilling Schottky's condition for ideal shot
noise.
