Probing unification scenarios with atomic clocks

We discuss the usage of measurements of the stability of nature’s fundamental constants coming from comparisons between atomic clocks as a means to constrain coupled variations of these constants in a broad class of unification scenarios. After introducing the phenomenology of these models, we provide updated constraints based on a global analysis of the latest experimental results. We obtain null results for the proton-to-electron mass ratio ??/?=(0.68±5.79)×10-16??yr-1 and for the gyromagnetic factor g?p/gp=(-0.72±0.89)×10-16??yr-1 (both of these being at the 95% confidence level). These results are compatible with theoretical expectations on unification scenarios, but much freedom exists due to the presence of a degeneracy direction in the relevant parameter space.