A vector model with a hybrid form of spacetime symmetry breaking consisting of explicit diffeomorphism breaking but spontaneous local Lorentz violation is presented. The combined effects of these symmetry breakings give rise to a theory obeying the Einstein-Maxwell equations in a preferred spatially homogeneous and isotropic frame, with photons emerging as massless Nambu-Goldstone modes. Interpretations and possible generalizations of this model are discussed, and comparisons are made to previous models describing photons as Nambu-Goldstone modes.

• Received 18 August 2015

DOI:https://doi.org/10.1103/PhysRevD.92.085015