Generalization of the Lagrange Expansion with Application to Physical Problems

Source abstract

Certain problems of fluid dynamics are conveniently discussed in the Lagrangian description by means of the displacement-vector function. The Eulerian variables describing the motion may be obtained from the displacement-vector function by a generalization of the Lagrange expansion which is here established. Two examples of the application of this expansion are given; the derivation of the Fokker-Planck equation, and the description of the surface conditions of a rippling electron stream by the device of equivalent surface charges.