Constraining Lorentz violation with cosmology
  The Einstein-Aether theory provides a simple, dynamical mechanism for breaking Lorentz invariance. It does so within a generally covariant context and may emerge from quantum effects in more fundamental theories. The theory leads to a preferred frame and can have distinct experimental signatures. In this letter, we perform a comprehensive study of the cosmological effects of the Einstein-Aether theory and use observational data to constrain it. Allied to previously determined consistency and experimental constraints, we find that an Einstein-Aether universe can fit experimental data over a wide range of its parameter space, but requires a specific rescaling of the other cosmological densities. 
J.A. Zuntz, P.G. Ferreira, T.G. Zlosnik