arXiv subjects

Victor V. Flambaum

Publications and source records attributed to Victor V. Flambaum.

57 records · Page 4Linked to original sources

arXiv2007

Comment on "Limits on the Time Variation of the Electromagnetic Fine-Structure Constant in the Low Energy Limit from Absorption Lines in the Spectra of Distant Quasars"

In their Letter [Phys. Rev. Lett. 92, 121302 (2004)] (also [Astron. Astrophys. 417, 853 (2004)]), Srianand et al. analysed optical spectra of heavy-element species in 23 absorption systems along background quasar sight-lines, reporting limits on relative variations in the fine-structure constant: da/a=(-0.06+/-0.06) x 10^{-5}. Here we demonstrate basic flaws in their analysis, using the same data and absorption profile fits, which led to spurious values of da/a and significantly underestimated uncertainties. We conclude that these data and fits offer no stringent test of previous evidence for a varying alpha. In their Reply (arXiv:0711.1742) to this Comment, Srianand et al. state or argue several points regarding their original analysis and our new analysis. We discuss these points here, dismissing all of them because they are demonstrably incorrect or because they rely on a flawed application of simple statistical arguments.

astro-ph↗

arXiv2007

Revision of VLT/UVES constraints on a varying fine-structure constant

We critically review the current null results on a varying fine-structure constant, alpha, derived from VLT/UVES quasar absorption spectra, focusing primarily on the many-multiplet analysis of 23 absorbers from which Chand et al. (2004) reported a weighted mean relative variation of da/a=(-0.06+/-0.06) x 10^{-5}. Our analysis of the same reduced data, using the same fits to the absorption profiles, yields very different individual da/a values with uncertainties typically larger by a factor of ~3. We attribute the discrepancies to flawed parameter estimation techniques in the original analysis and demonstrate that the original da/a values were strongly biased towards zero. Were those flaws not present, the input data and spectra should have given a weighted mean of da/a=(-0.44+/-0.16) x 10^{-5}. Although this new value does reflect the input spectra and fits (unchanged from the original work -- only our analysis is different), we do not claim that it supports previous Keck/HIRES evidence for a varying alpha: there remains significant scatter in the individual da/a values which may stem from the overly simplistic profile fits in the original work. Allowing for such additional, unknown random errors by increasing the uncertainties on da/a to match the scatter provides a more conservative weighted mean, da/a=(-0.64+/-0.36) x 10^{-5}. We highlight similar problems in other current UVES constraints on varying alpha and argue that comparison with previous Keck/HIRES results is premature.

astro-ph↗

arXiv1998

A Search for Time Variation of the Fine Structure Constant

A method offering an order of magnitude sensitivity gain is described for using quasar spectra to investigate possible time or space variation in the fine structure constant, alpha. Applying the technique to a sample of 30 absorption systems, spanning redshifts 0.5 < z< 1.6, obtained with the Keck I telescope, we derive limits on variations in alpha over a wide range of epochs. For the whole sample Delta(alpha)/alpha = -1.1 +/- 0.4 x 10^{-5}. This deviation is dominated by measurements at z > 1, where Delta(alpha)/alpha = -1.9 +/- 0.5 x 10^{-5}. For z < 1, Delta(alpha)/alpha = -0.2 +/- 0.4 x 10^{-5}, consistent with other known constraints. Whilst these results are consistent with a time-varying alpha, further work is required to explore possible systematic errors in the data, although careful searches have so far not revealed any.

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