80 likes | 537 Views
(Homogeneous equations satisfied if ). Lagrangian for E&M Fields. Equations we would like to see emerge from Lagrangian. Maxwell’s inhomogeneous equations:. Energy Density:. Momentum flow:. Constraint: Gauge Invariance of Lagrangian.
E N D
(Homogeneous equations satisfied if ) Lagrangian for E&M Fields Equations we would like to see emerge from Lagrangian Maxwell’s inhomogeneous equations: Energy Density: Momentum flow: Constraint: Gauge Invariance of Lagrangian
Normal Type Lagrangian Density Normal Kinetic Term for Fields: However, not gauge invariant If and You get gauge invariance back. Note, in Lorentz gauge Total divergences don’t contribute to action
E&M Lagrangian Equations of motion Inhomogeneous Maxwell’s equations
Stress Energy Tensor Not obviously symmetric (but can be made so in the absence of sources – see Goldstein, p. 583) Total divergences – go to zero in surface integration for currents Not symmetric: angular momentum conservation?