Planck-scale constraints on anisotropic Lorentz and CPT invariance violations from optical polarization measurements

Understand

Lorentz invariance is the fundamental symmetry of Einstein's theory of special relativity, and has been tested to great level of detail.

• However, theories of quantum gravity at the Planck scale indicate that Lorentz symmetry may be broken at that scale motivating further tests.
• While the Planck energy is currently unreachable by experiment, tiny residual effects at attainable energies can become measurable when photons propagate over sufficiently large distances.
• The Standard-Model Extension (SME) is an effective field theory approach to describe low-energy effects of quantum gravity theories.