Concatenating Variational Principles and the Kinetic Stress-Energy-Momentum Tensor

Abstract

We show how to "concatenate" variational principles over dierent bases into one over a single base, thereby providing a unied Lagrangian treatment of interacting systems. As an example we study a Klein{ Gordon eld interacting with a mesically charged particle. We employ our method to give a novel group-theoretic derivation of the kinetic stress-energy-momentum tensor density corresponding to the particle.