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 ${ ̇ {}}{{μ}}/{μ}=(0.68±{}5.79)×{}{10}^{{-}16} {yr}^{{-}1}$ and for the gyromagnetic factor ${{ ̇ {}}{g}}ₚ/{g}ₚ=({-}0.72±{}0.89)×{}{10}^{{-}16} {yr}^{{-}1}$ (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.