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Bopp-Podolsky Scalar Electrodynamics Propagators and Energy-Momentum Tensor in Covariant and Light-Front Coordinates

We consider the interaction between a charged scalar boson and the Bopp-Podolsky gauge fields. The Bopp-Podolsky (BP) electrodynamics possesses both massive and massless propagation modes for the photon, while preserving gauge invariance. We obtain the propagator of all fields present in the model for the higher-order generalizations of the linear covariant, light-front and doubly transverse light-front gauges. Although BP's original model is described by a higher-order derivatives Lagrangian, it is possible to work with an equivalent reduced-order version by means of the introduction of an auxiliary vector field. We compute the gauge-invariant improved energy-momentum tensor for the full reduced-order interacting BP model. Besides the more traditional front-form view, we also discuss the light-front perspective in both versions of the model. Within a Lagrangian framework approach we maintain explicit covariance at all steps and show that the field propagators, as well as the energy-momentum tensor, can be cast into a light-front closed form using specific properties of general coordinate transformations.