Lagrangian Formalism on Jet-Gauge and Jet-Diffeomorphism Groups: Towards   a Unification of Gravity with Internal Gauge Interactions
  In this talk the description of gauge theories associated with internal symmetries is extended to the case in which the symmetry group is the space-time translation group (recovering Einstein's theory) using the standard jet-bundle formalism. We also reformulate these theories introducing the idea of jet-gauge and jet-diffeomorphism groups. Finally, we attempt to a simple, yet non-trivial, mixing of gravity and electromagnetism (or more general internal interaction) by turning to gauge symmetry a central extension of the Poincare group. 
V. Aldaya, E. Sanchez-Sastre