Noether?s theorems and the energy-momentum tensor in quantum gauge theories

Noether's first and second theorems both imply conserved currents that can be identified as an energy -momentum tensor (EMT). The first theorem identifies the EMT as the conserved current associated with global spacetime translations, while the second theorem identifies it as a conserved current associated with local spacetime translations. This work obtains an EMT for quantum electrodynamics and quantum chromodynamics through the second theorem, which is automatically symmetric in its indices and invariant under the expected symmetries [e.g., Becchi-Rouet-Stora-Tyutin (BRST) invariance] without the need for introducing an ad hoc improvement procedure.

Automated summary

This study obtains the energy-momentum tensor for quantum electrodynamics and quantum chromodynamics through Noether's second theorem, and it has automatic symmetry and invariance.