Momentum Routing Invariance in Extended QED: Assuring Gauge Invariance Beyond Tree Level

Understand

We address the study of gauge invariance in the Standard Model Extension which encompasses all Lorentz-violating terms originated by spontaneous symmetry breaking at the Planck scale.

• In particular, we fully evaluate Ward identities involving two and three point functions and derive the conditions which assure gauge invariance of the electromagnetic sector of the Standard Model Extension at one-loop.
• We show that momentum routing invariance is sufficient to fix arbitrary and regularization dependent parameters intrinsic to perturbation theory in the diagrams involved.
• A scheme which judiciously collects finite but undetermined quantum corrections is employed, a particularly subtle issue in the presence of $\gamma_5$ matrices.