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 ${\dot\mu}/{\mu}=(0.68\pm5.79)\ti mes10^{-16}\, {\rm yr}{}^{-1}$ and for the gyromagnetic factor ${\dot g_p}/{g_p} =(-0.72\pm0.89)\times10^{-16}\, {\rm yr}{}^{-1}$ (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. 
M.C. Ferreira, M.D. Juli\~ao, C.J.A.P. Martins and A.M.R.V.L. Monteiro
hep-ph astro-ph.CO hep-th physics.atom-ph