Direct Terrestrial Test of Lorentz Symmetry in Electrodynamics to 10$^{-18}$

TL;DR

This paper reports the most precise terrestrial test of Lorentz symmetry in electrodynamics, using ultra-stable oscillators to constrain potential violations at the 10^{-18} level, supporting Lorentz invariance.

Contribution

It presents a highly sensitive Michelson-Morley experiment that improves bounds on Lorentz violation in photon behavior by an order of magnitude.

Findings

No significant Lorentz violations detected.

Constrained Lorentz-violating parameters to 10^{-18} level.

Set bounds on nine anisotropies of the speed of light.

Abstract

Lorentz symmetry is a foundational property of modern physics, underlying the standard model of particles and general relativity. It is anticipated that these two theories are low energy approximations of a single theory that is unified and consistent at the Planck scale. Many unifying proposals allow Lorentz symmetry to be broken, with observable effects appearing at Planck-suppressed levels; thus precision tests of Lorentz invariance are needed to assess and guide theoretical efforts. Here, we use ultra-stable oscillator frequency sources to perform a modern Michelson-Morley experiment and make the most precise direct terrestrial test to date of Lorentz symmetry for the photon, constraining Lorentz violating orientation-dependent relative frequency changes $\Delta\nu$/$\nu$ to 9.2$\pm$10.7$\times10^{-19}$ (95$\%$ confidence interval). This order of magnitude improvement over previous Michelson-Morley experiments allows us to set comprehensive simultaneous bounds on nine boost and rotation anisotropies of the speed of light, finding no significant violations of Lorentz symmetry.