Nonlocal Lagrange formalism in the thermodynamics of irreversible processes: variational procedures for kinetic equations

This paper is concerned with generalizations of the known local Lagrange formalism of first order. It will be applied to kinetic equations like the Fokker-Planck equation and the Boltzmann equation. In the latter case nonlocal methods are necessary from the very beginning. Nevertheless, in the framework of Fréchetʹs formalism the calculations are as easy as in the classical local case. Furthermore, a rather general entropy concept can be established within nonlocal Lagrange formalism for irreversible systems. As a main result of this paper we derive within our general concept the known entropy balances of the Boltzmann theory and the Fokker-Planck theory, respectively. It will be emphasized that our general concept may be applied to a very wide class of irreversible systems, in principle.