I have studied Jackson, Landau, and Barut textbooks on electrodynamics, together with Weinberg's Gravitation and Cosmology textbook, and I find that the usual action(adsbygoogle = window.adsbygoogle || []).push({});

[itex]S = S_f + S_m + S_{mf}[/itex]

is inconsistent and not well-defined. For instance, what is the meaning of [itex]S_f[/itex]? A free-field term? Or an interacting-field term that diverges?

Moreover, the derivations of the energy-momentum tensors from the above action seem ad-hoc. For instance, Landau & Lifgarbagez just claim that during the derivation one mustassumethat the particles are non-interacting! That is, one mustignorethe [itex]S_{mf}[/itex] term.

All of this mess is confirmed by papers as that by Feynman & Wheeler [1] and by Chubykalo & Smirnov-Rueda [2] where alternative actions are proposed to correct the deficiencies. However, I find still difficulties with those actions and no systematic procedure to get the corresponding energy-momentum tensors.

Does exist some well-defined and consistent action for electrodynamics leading to a well-defined and physically correct energy-momentum tensor?

[1] Rev. Mod. Phys. 1949: 21(3), 425.

[2] Phys. Rev. E 1996: 53(5), 5373. [Erratum] Phys. Rev. E 1997: 55(3), 3793.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# What is the electrodynamic action and its energy-momentum tensor?

**Physics Forums | Science Articles, Homework Help, Discussion**