Related papers: Constraints on changes in fundamental constants fr…

We report deep Green Bank Telescope spectroscopy in the redshifted HI 21cm and OH 18cm lines from the $z = 0.765$ absorption system towards PMN J0134-0931. A comparison between the "satellite" OH 18cm line redshifts, or between the…

We describe a new technique to estimate variations in the fundamental constants using 18cm OH absorption lines. This has the advantage that all lines arise in the same species, allowing a clean comparison between the measured redshifts. In…

We report the detection of the satellite 18 cm OH lines at 1612 and 1720 MHz in the z=0.2467 molecular absorption system toward the radio source PKS 1413+135. The two OH lines are conjugate; the 1612 MHz line is seen in absorption while the…

We have used the Arecibo Telescope to carry out one of the deepest-ever integrations in radio astronomy, targetting the redshifted conjugate satellite OH 18 cm lines at $z \approx 0.247$ towards PKS1413+135. The satellite OH 1720 and 1612…

We have detected narrow HI 21cm and CI absorption at $z \sim 1.4 - 1.6$ towards Q0458$-$020 and Q2337$-$011, and use these lines to test for possible changes in the fine structure constant $\alpha$, the proton-electron mass ratio $\mu$, and…

We describe a new technique to measure variations in the fundamental parameters $\alpha$ and $y \equiv m_e/m_p$, using the sum of the frequencies of cm-wave OH ``main'' lines. The technique is $\sim$ three orders of magnitude more sensitive…

The study of redshifted spectral lines can provide a measure of the fundamental constants over large look-back times. Current grand unified theories predict an evolution in these constants and astronomical observations offer the only…

We report Westerbork Synthesis Radio Telescope and Arecibo Telescope observations of the redshifted satellite OH-18cm lines at $z \sim 0.247$ towards PKS1413+135. The "conjugate" nature of these lines, with one line in emission and the…

Absorption-line systems detected in high resolution quasar spectra can be used to compare the value of dimensionless fundamental constants such as the fine-structure constant, alpha, and the proton-to-electron mass ratio, mu = m_p/m_e, as…

We summarize the attempts by our group and others to derive constraints on variations of fundamental constants over cosmic time using quasar absorption lines. Most upper limits reside in the range 0.5-1.5x10-5 at the 3sigma level over a…

Aims. To obtain limits on the variation of the fine-structure constant alpha and the electron-to-proton mass ratio mu over different cosmological epochs. Methods. A new approach based on the comparison of redshifts of far infrared (FIR)…

We have detected the two 18cm OH satellite lines from the $z \sim 0.247$ source PKS1413+135, the 1720 MHz line in emission and the 1612 MHz line in absorption. The 1720 MHz luminosity is $L_{\rm OH} \sim 354 L_\odot$, more than an order of…

We present deep GMRT OH and WSRT HI absorption spectra of the $z = 0.6846$ gravitational lens toward B0218+357. Both the 1665 MHz and 1667 MHz OH lines are clearly detected for the first time while a new wide absorption component was…

Nine quasar absorption spectra at 21-cm and UV rest-wavelengths are used to estimate possible variations in x=alpha^2 g_p mu, (alpha is the fine structure constant, g_p the proton g-factor and mu=me/mp the electron-to-proton mass ratio). We…

OH absorption is currently the only viable way to detect OH molecules in non-masing galaxies at cosmological distances. There have been only 6 such detections at z>0.05 to date and so it is hard to put a statistically robust constraint on…

We investigate the constraints that OH microwave transitions in megamasers and molecular absorbers at cosmological distances may place on the evolution of the fine structure constant alpha=e^2/(hbar c). The centimeter OH transitions are a…

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…

QSO absorption spectra provide an extremely useful probe of possible cosmological variation in various physical constants. Comparison of H I 21cm absorption with corresponding molecular (rotational) absorption spectra allows us to constrain…

(Abridged) Many-multiplet (MM) method applied to three inhomogeneous samples of Keck/HIRES quasar absorption spectra gives a shift in the value of the fine-structure constant of Delta alpha/alpha = (-5.4+/-1.2) 10^{-6} in the redshift range…

We present a short review of the current quasar (QSO) absorption line constraints on possible variation of the fine structure constant, alpha = e^2/(hbar*c). Particular attention is paid to recent optical Keck/HIRES spectra of 49 absorption…