Noether’s theorems and conserved currents in gauge theories in the presence of fixed fields
Oct 11, 201617 pages
Published in:
- Phys.Rev.D 96 (2017) 2, 025018
- Published: Jul 24, 2017
e-Print:
- 1610.03281 [gr-qc]
View in:
Citations per year
Abstract: (APS)
We extend the standard construction of conserved currents for matter fields in general relativity to general gauge theories. In the original construction, the conserved current associated with a spacetime symmetry generated by a Killing field hμ is given by -gTμνhν, where Tμν is the energy-momentum tensor of the matter. We show that if in a Lagrangian field theory that has gauge symmetry in the general Noetherian sense some of the elementary fields are fixed and are invariant under a particular infinitesimal gauge transformation, then there is a current Bμ that is analogous to -gTμνhν and is conserved if the nonfixed fields satisfy their Euler-Lagrange equations. The conservation of Bμ can be seen as a consequence of an identity that is a generalization of ∇μTμν=0 and is a consequence of the gauge symmetry of the Lagrangian. This identity holds in any configuration of the fixed fields if the nonfixed fields satisfy their Euler-Lagrange equations. We also show that Bμ differs from the relevant canonical Noether current by the sum of an identically conserved current and a term that vanishes if the nonfixed fields are on shell. For an example, we discuss the case of general, possibly fermionic, matter fields propagating in fixed gravitational and Yang-Mills background. We find that in this case the generalization of ∇μTμν=0 is the Lorentz law ∇μTμν-FaνλJaλ=0, which holds as a consequence of the diffeomorphism, local Lorentz and Yang-Mills gauge symmetry of the matter Lagrangian. For a second simple example, we consider the case of general fields propagating in a background that consists of a gravitational and a real scalar field.Note:
- 28 pages, LaTeX, minor changes, journal reference added
- symmetry: gauge
- current: conservation law
- matter: symmetry
- symmetry: Noether
- current: Noether
- background: Yang-Mills
- transformation: gauge
- symmetry: space-time
- diffeomorphism: invariance
- tensor: energy-momentum
References(57)
Figures(0)
- [1]
- [2]
- [3]
- [4]
- [5]
- [6]
- [7]
- [8]
- [9]
- [11]
- [12]
- [13]
- [14]
- [15]
- [16]
- [17]
- [18]
- [19]
- [20]
- [21]
- [22]
- [23]
- [24]
- [25]
- [26]