Submitter: | Neeraj Gupta |

Description: | Most of the successful physical theories rely on the constancy of a few fundamental quantities such as the fine structure constant, the proton-to-electron mass ratio, etc. Some modern theories of high energy physics that try to unify the fundamental interactions predict the variation of these dimensionless fundamental constants over cosmological scales. Although current laboratory constraints exclude any significant variation of these constants over solar system scales and on geological time scales, it is not observationally/ experimentally excluded that they vary over cosmological scales. In a paper, now accepted for publication, we use the 21-cm and metal absorption lines detected in the high resolution spectra of 5 quasars obtained with the GBT, GMRT and VLT to constrain the combined variation of the fine structure constant (α), the proton-to-electron mass ratio (μ) and the proton gyromagnetic factor (g_p). We find the weighted and the simple means of Δx/x to be respectively −(0.1 ± 1.3)×10^−6 and (0.0 ± 1.5)×10^−6 at the mean redshift of z = 1.36 corresponding to a look back time of 9 Gyr. This is the most stringent constraint ever obtained on Δx/x. If we only use the two systems towards quasars unresolved at milliarcsecond scales, we get the simple mean of Δx/x = +(0.2±1.6)×10^−6. Assuming constancy of other constants we get Δα/α = (0.0 ± 0.8)×10^−6 which is a factor of two better than the best constraints obtained so far. On the other hand assuming α and g_p have not varied we derive Δμ/μ = (0.0 ± 1.5)×10^−6 which is again the best limit ever obtained on the variation of μ over this redshift range. "Constraining the variation of fundamental constants at z ~ 1.3 using 21-cm absorbers" H. Rahmani, R. Srianand, N. Gupta, P. Petitjean, P. Noterdaeme, and D. Albornoz Vasquez, MNRAS accepted http://adsabs.harvard.edu/abs/2012arXiv1206.2653R |

Copyright: | Neeraj Gupta |

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