Search for Lorentz violation using experiments measuring neutron electric dipole moment*

Lorentz symmetry is a cornerstone of both general relativity (GR) and the standard model (SM). It ensures that the physical laws are invariant under rotations and boosts. Both GR and the SM are considered to be low energy limits of a more fundamental theory at the Plank scale. Many such theories at the Plank scale spontaneously violate the Lorentz symmetry, even though no such violation has ever been experimentally verified. However, violations of Lorentz symmetry have already been incorporated into an effective field theory known as the standard model extension. Measurement of a statistically significant cosmic anisotropic field such as a: magnetic field, $\tilde{b}$, magnetic moment, $\mu_{ij}$, or an electric dipole moment, $d_{ij}$, are all indications for the violation of Lorentz symmetry.

Experiments measuring electric dipole moments of fundamental particles usually measure the precession frequencies, of the particles, under the influence of magnetic and electric fields. Such measurements are sensitive to any cosmic anisotropic fields, owing to their modulating effects upon the measurable of precession frequencies. Furthermore, a gravitational dipole moment for a particle also induces similar modulation of precession frequency, and therefore a constraint on Lorentz violating fields may also be used to limit the gravitational dipole moment. An updated sensitivity study to such anisotropic fields will be discussed, considering the most recent neutron electric dipole moment search.