3 papers
gr-qc2026
Covariant conservation laws, local invariance and Noether's second theorem
Nuno Barros e Sá, Miguel A. S. Pinto, Tomás Trindade
We lay down a set of requirements for a field theory to produce a covariant conservation law out of Noether's second theorem, and show that neither local invariance implies a covar…
gr-qc2025
Dirac bracket and time dependent constraints
Nuno Barros e Sá
We provide a simultaneous derivation of the Dirac bracket and of the equations of motion for second-class constrained systems when the constraints are time-dependent. The necessity…
math-ph2025
Improper currents in theories with local invariance
Nuno Barros e Sá
We present a proof that the currents arising from Noether's first theorem in a physical theory with local invariance can always be decomposed into two terms, one of them vanishing…