Conserved currents from nonlocal constants in relativistic scalar field theories

Nonlocal constants are functions that are constant along motion but whose value depends on the past history of the motion itself. They have been introduced to study ODEs and, among all applications, they provide first integrals in special cases. In this respect, a new approach to get nonlocal constants within the framework of Lagrangian scalar field theory is introduced. We derive locally-conserved currents from them, and we prove the consistency of our results by recovering some standard Noetherian results. Applications include the real/complex nonlinear interacting theory and the real dissipative Klein–Gordon theory.