Nissim Kanekar

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We describe a new technique to estimate variations in the fundamental constants using 18 cm OH absorption lines, with the advantage that all lines arise in the same species, allowing a clean comparison between the measured redshifts. In conjunction with one additional transition, it is possible to simultaneously measure changes in alpha, g(p), and y(More)
We report Karl G. Jansky Very Large Array (VLA) absorption spectroscopy in four methanol (CH3OH) lines in the z = 0.885 82 gravitational lens towards PKS1830−211. Three of the four lines have very different sensitivity coefficientsKμ to changes in the proton–electron mass ratio μ; a comparison between the line redshifts thus allows us to test for temporal(More)
We report results from a deep search for redshifted HI 21cm absorption in 55 strong MgIIλ2796 absorbers (having Wλ2796 0 > 0.5Å) at intermediate redshifts, 0.58 < zabs < 1.70, with the Green Bank Telescope (GBT) and the Giant Metrewave Radio Telescope (GMRT). Nine detections of HI 21cm absorption were obtained, all at 1.17 < zabs < 1.68, including three(More)
We have detected the two 18 cm OH satellite lines from the z approximately 0.247 source PKS1413+135, the 1720 MHz line in emission and the 1612 MHz line in absorption. The 1720 MHz luminosity is L(OH) approximately 354L (center dot in circle), more than an order of magnitude larger than that of any other known 1720 MHz maser. The profiles of the two(More)
We investigate the evolution of nonlinear density perturbations by taking into account the effects of shear and angular momentum of the system. Starting from the standard spherical top hat model in which these terms are ignored, we introduce a physically motivated closure condition which specifies the dependence of these terms on δ. The modified equation(More)
We report the detection of redshifted HI 21cm absorption in the z ∼ 2.347 damped Lymanα absorber (DLA) towards PKS B0438−436, with the Green Bank Telescope. This is the second-highest redshift at which 21cm absorption has been detected in a DLA. The absorption extends over ∼ 60 km s and has two distinct components, at z = 2.347477(12) and z = 2.347869(20).(More)