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[1008.3907] Evidence for spatial variation of the fine structure constant
 
Authors:J. K. Webb, J. A. King, M. T. Murphy, V. V. Flambaum, R. F. Carswell, M. B. Bainbridge
Abstract:We previously reported observations of quasar spectra from the Keck telescope suggesting a smaller value of the fine structure constant, alpha, at high redshift. A new sample of 153 measurements from the ESO Very Large Telescope (VLT), probing a different direction in the universe, also depends on redshift, but in the opposite sense, that is, alpha appears on average to be larger in the past. The combined dataset is well represented by a spatial dipole, significant at the 4.1 sigma level, in the direction right ascension 17.3 +/- 0.6 hours, declination -61 +/- 9 degrees. A detailed analysis for systematics, using observations duplicated at both telescopes, reveals none which are likely to emulate this result.
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Joe Whitbourn



Joined: 28 Jul 2010
Posts: 2
Affiliation: Durham University

PostPosted: August 25 2010  Reply with quote

This Paper claims a detection a dipole in the value of α at 4.1σ

By using both the Keck and the VLT they seem pretty confident in having eliminated/understood the instrument systematics in what looks like a difficult measurement. Their data seems self consistent, in the worse case scenario the result is still 3.1σ

If true it's a huge result, the equivalence principle is at stake. But why a dipole?

Any comments?
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Ben Weiner



Joined: 01 Sep 2010
Posts: 3
Affiliation: Steward

PostPosted: September 01 2010  Reply with quote

The 64 dollar question in these measurements has always been, would the VLT/UVES sample confirm the change in alpha measured in the Keck/HIRES sample, when the two samples are processed the same way? Such a confirmation would rule out systematics due to subtle inaccuracies in the wavelength scale of the spectrographs, since the systematics should be different for the two instruments.

This question has now been answered.
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Rainer W. Kühne



Joined: 30 Oct 2010
Posts: 10
Affiliation: unemployed

PostPosted: November 02 2010  Reply with quote

Spatial variation of the fine-structure constant?

J. K. Webb et al., arXiv: 1008.3907v1 presented possible evidence of a spatial variation of the fine-structure constant, where the axis of the dipole points to R. A. = 17.3h, dec. = −61°.

Such a spatial variation, if confirmed, might indicate an anisotropic universe. I would like to point out two earlier works which reported possible evidence of an anisotropic universe.

P. Birch, Nature 298 (1982) 451−454 presented possible evidence of a vorticity of the universe, where the axis of the dipole points to R. A. = 14h 55min, dec. = −35°.

Only a small part of the 3K dipole can be explained by the motion of the Sun around the Galactic centre and the gravitational infall of the Milky Way into the Virgo cluster of galaxies. A. Dressler, Nature 350 (1991) 391−397 suggested a motion of the Local Supercluster towards Galactic longitude l = 307° and Galactic latitude b = 9° (approximately R. A. = 13.5h, dec. = −45°). His claimed Great Attractor has never been detected. So it is possible that this so far unexplained part of the 3K dipole results not from Local Supercluster motion, but from an anisotropic universe.

The three directions listed above differ from one another. However, the error bars are large. Possibly the works of Birch, Dressler, and Webb et al. support an anisotropic universe.

Anyone who is interested in my early work on an anisotropic universe is invited to read my paper R. W. Kühne, Mod. Phys. Lett. A 12 (1997) 2473−2474 = arXiv: astro-ph/9708109. In it I argued that the alignment of the rotation axes of the galaxies of the Perseus-Pisces supercluster results from universal vorticity (Gödel cosmology).

Anyone who is interested in my early work on a time-variation of the fine-structure constant is invited to read my paper R. W. Kühne, Mod. Phys. Lett. A 14 (1999) 1917−1922 = arXiv: astro-ph/9908356.
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Maciej Bilicki



Joined: 12 May 2010
Posts: 19
Affiliation: University of Cape Town

PostPosted: November 03 2010  Reply with quote

The evidence that the dipole of CMB temperature is of kinematic origin is quite strong I would say. An example is that for at least two decades people are getting a small misalignment angle between this dipole and the one of galaxy clustering (Strauss et al. 1992, Maller et al. 2003, Erdogdu et al. 2005 to mention just a few). This clustering dipole, which is a measure of the peculiar gravitiaional acceleration of the Local Group, has been calculated from many different samples, including IRAS data, optical data, 2MASS data, Xray data etc., and the results are quite consistent: the angle is of the order of 10−20 deg.

The alignment of the two vectors is very well predicted by linear theory of gravitational instability in Friedmann models (some misalignment is of course expected e.g. due to nonlinearities). Do the anisotropic models predict the same? If they do, then of course this doesn't help.

Still, I wouldn't expect one single attractor to induce our motion. Especially that evidence seems to appear that some of those attractors may be very remote (e.g. X-ray clustering dipole of Kocevski & Ebelling 2006 or bulk flows of Watkins, Feldman & Hudson 2009).
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Rainer W. Kühne



Joined: 30 Oct 2010
Posts: 10
Affiliation: unemployed

PostPosted: November 03 2010  Reply with quote

I agree that according to recent studies the Local Supercluster (region within 50 Mpc or cz = 3500 km/s) shows a bulk flow with 495 km/s towards l = 275°, b = 12° (Sandage et al.) or with 407 +- 81 km/s towards l = 287°, b = 8° (Watkins et al.).

If this bulk flow results from density fluctuations of scales 3500 km/s < cz < 300 000 km/s, then one has difficulties to agree this with the observed multipole anisotropies of the cosmic microwave background radiation.

"Taken together the data suggest that the bulk flow within a Gaussian window of radius 50 h−1 Mpc is 407 ± 81 km s−1 toward l= 287°± 9°, b= 8°± 6°. The large-scale bulk motion is consistent with predictions from the local density field. This indicates that there are significant density fluctuations on very large scales. A flow of this amplitude on such a large scale is not expected in the WMAP5 (Wilkinson Microwave Anisotropy Probe) normalized Λ cold dark matter cosmology, for which the predicted one-dimensional rms velocity is ∼110 km s−1. The large amplitude of the observed bulk flow favours the upper values of the WMAP5 Ωmh2–σ8 error-ellipse, but even the point at the top of the WMAP595 per cent confidence ellipse predicts a bulk flow which is too low compared to that observed at >98 per cent confidence level." (from the abstract of Watkins et al.)

A. Sandage, B. Reindl, G. Tammann, Astrophys. J. 714 (2010) 1441−1459.
R. Watkins. H. A. Feldman, M. J. Hudson, Mon. Not. Roy. Astron. Soc. 392 (2009) 743−756.
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