Necessary criterion of choosing the energy-momentum tensor and the Lagrange formalism
arXiv:1904.10297
Abstract
It is shown that the necessary criterion for choosing the energy-momentum tensor of a physical system is the form of its linear invariant, which should be the lagrangian of this physical system. Examples of energy-momentum tensors that meet this criterion are given. For an electromagnetic field in vacuum, the linear invariant of the energy-momentum tensor must be the canonical lagrangian or the quadratic invariant of the electromagnetic field tensor. A mathematical method for obtaining the lagrangian that complements the Lagrange formalism is proposed.
6 pages