AMO
In the literature: open
Are electron-sector Lorentz-violation coefficients nonzero at 1e-23?
In plain words
If space had a preferred direction, an electron moving in an atom would have slightly different energy depending on how the atom is oriented as the Earth rotates. Clocks with oddly shaped electron orbitals are the most sensitive detectors of this.
Precise statement
In the Standard-Model Extension, the electron coefficients $c_{JK}$ (traceless symmetric) are bounded at about 1e-21 by Yb+ E3 clock comparisons with orthogonal quantization axes (Sanner et al 2019). Determine whether any $c_{JK}$ is nonzero at the 1e-23 level using highly charged ions or Dy and Yb+ states with large anisotropic momentum operators.
What would settle it
Sidereal-modulation analysis of a clock comparison with anisotropy sensitivity enhanced by more than 100 over Yb+ E3.