Robust laboratory limits on a cosmological spatial gradient in the electromagnetic fine-structure constant from accelerometer experiments

Quasar absorption spectral data indicate the presence of a spatial gradient in the electromagnetic fine-structure constant alpha on cosmological length scales. We point out that experiments with accelerometers, including torsion pendula and atom interferometers, can be used as sensitive probes of cosmological spatial gradients in the fundamental constants of nature, which give rise to equivalence-principle-violating forces on test masses. Using laboratory data from the Eot-Wash experiment, we constrain spatial gradients in alpha along any direction to be vertical bar del alpha/alpha vertical bar < 6.6 x 10(-4) (Glyr)(-1) at 95% confidence level. Our result represents an order of magnitude improvement over laboratory bounds from clock-based searches for a spatial gradient in alpha directed along the observed cosmological alpha-dipole axis. Improvements to accelerometer experiments in the foreseeable future are expected to provide sufficient sensitivity to test the cosmological alpha dipole seen in astrophysical data.

Automated summary

Quasar absorption spectral data suggest the presence of a spatial gradient in the electromagnetic fine-structure constant alpha on cosmological scales. Accelerometer experiments can serve as sensitive probes of such gradients, with laboratory data indicating potential for improved sensitivity in the future.