Constraints on Space-Time Torsion from Hughes-Drever Experiments

The coupling of space-time torsion to the Dirac equation leads to effects on the energy levels of atoms which can be tested by Hughes-Drever type experiments. Reanalysis of these experiments carried out for testing the anisotropy of mass and anomalous spin couplings can lead to the till now tightest constraint on the axial torsion by $K \leq 1.5 . 10^{-15} m^{-1}$.