Lorentz-Violating Electrodynamics and the Cosmic Microwave Background

Possible Lorentz-violating effects in the cosmic microwave background are studied. We provide a systematic classification of renormalizable and nonrenormalizable operators for Lorentz violation in electrodynamics and use polarimetric observations to search for the associated violations.

Figure 1

Sample plots of likelihood versus values of coefficients for Lorentz violation. For each listed coefficient, the boxes indicate numerically calculated values, and the curve is a smooth extrapolation through them. Dark-gray and light-gray regions represent the 68% and 95% confidence levels, respectively.