  We show that a completely orthodox and conserving Landau-Silin approach to
current fluctuations in quantum point contacts accounts for the major, and as
yet unexplained, peak structures observed in the QPC experiment of Reznikov et
al. [Phys. Rev. Lett. 75, 3340 (1995)], for constant values of source-drain
current. Those features are absent from corresponding phenomenological
predictions and are unanticipated by Landauer-Buettiker theory. The kinetic
origin of the Reznikov et al. noise peaks directly manifests the action of the
compressibility sum rule in the electron gas. This rule, in turn, is the
outworking of microscopic gauge invariance.
