A stringent constraint on the fractional change of proton g-factor

Abstract

We report a constraint on the cosmological variation of the proton g-factor, $g_p$. By comparing the measured redshifts between \mbox{H\,{\sc i}} 21 cm and OH 18 cm lines observed with the newly commissioned Five-hundred-meter Aperture Spherical radio Telescope (FAST) toward PKS 1413+135 at $z$ = 0.24671, we obtain $\hat{I}”g_p/g_p=(-4.3\pm 2.5)\times 10^{-5}$, which is more than two orders of magnitude more sensitive than previous constraints. In addition, we obtain sensitive constraints of $\hat{I}”(\hat{I}¼\hat{I}{\pm }^2)/(\hat{I}¼\hat{I}{\pm }^2)=(2.0\pm 1.2)\times 10^{-5}$ and $\hat{I}”(\hat{I}¼\hat{I}{\pm }^2{g}_p^{0.64})/(\hat{I}¼\hat{I}{\pm }^2{g}_p^{0.64})=(-4.7\pm 1.9)\times 10^{-6}$.

2 figures, 1 table, accepted for publication on SCIENCE CHINA Physics, Mechanics & Astronomy