We extend the least action principle to continuum systems. The data for the new principle consists of the intensity of the wave (or rather the wave action) at two instances of time. We define an appropriate Lagrangian, and formulate a variational problem in terms of it. The critical points of the functional are used to determine the wave’s phase. The theory is applicable to the semiclassical li...

The basic driving unit of oscillatory electrical activity in stomach and intestine is the slow wave, a propagating depolarization of myogenic origin. The slow wave controls contractile activity in the intestine by triggering action potential bursts, while in the stomach there is both action potential and spike-free slow wave activation. This review attempts to summarize recent characterizations...

Approximate surface fields due to a plane-wave solution and a local-mode solution are compared. The plane-wave solution, which is new, is shown to agree well with experiment. The local-mode solution, which often has been applied to tapered waveguides and antennas, fails near the cutoffs of the surface waves.