New limits on coupling of fundamental constants to gravity using 87Sr optical lattice clocks

The (1)S(0)-(3)P(0) clock transition frequency nu(Sr) in neutral (87)Sr has been measured relative to the Cs standard by three independent laboratories in Boulder, Paris, and Tokyo over the last three years. The agreement on the 1x10(-15) level makes nu(Sr) the best agreed-upon optical atomic frequency. We combine periodic variations in the (87)Sr clock frequency with (199)Hg(+) and H-maser data to test local position invariance by obtaining the strongest limits to date on gravitational-coupling coefficients for the fine-structure constant alpha, electron-proton mass ratio mu, and light quark mass. Furthermore, after (199)Hg(+), (171)Yb(+), and H, we add (87)Sr as the fourth optical atomic clock species to enhance constraints on yearly drifts of alpha and mu.