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Traces of ‘Mythical’ Cosmic Strings Found

  1. Jan 24, 2008 #1

    SF

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    controversial new study indicates that there are traces of vast cosmic strings left over in radiation from the early universe. If indeed confirmed to be real, these cosmic strings would offer an unprecedented window into the extreme physics of origins of the universe.

    The idea is that snags in the fabric of space may have developed a fraction of a second after the universe's birth. This would have likely occurred at the end of the period called inflation when the universe was rapidly expanding.

    These “snags” are thought to be shaped like very slender strings, with a thickness much less than the width of an atom but with lengths that can be measured in light years. They would also be incredibly heavy. A section just a kilometer long would potentially have as much mass as the entire Earth.

    http://www.dailygalaxy.com/my_weblog/2008/01/traces-of-mythi.html
     
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  3. Jan 24, 2008 #2

    marcus

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    I think the "Daily Galaxy" popularized account refers to this paper by Bevis and Hindmarsh and others
    http://arxiv.org/abs/0711.1842
    Cosmic microwave anisotropies from BPS semilocal strings
    Authors: Jon Urrestilla, Neil Bevis, Mark Hindmarsh, Martin Kunz, Andrew R. Liddle
    (Submitted on 12 Nov 2007)

    Abstract: We present the first ever calculation of cosmic microwave background CMB anisotropy power spectra from semilocal cosmic strings, obtained via simulations of a classical field theory. Semilocal strings are a type of non-topological defect arising in some models of inflation motivated by fundamental physics, and are thought to relax the constraints on the symmetry breaking scale as compared to models with (topological) cosmic strings. We derive constraints on the model parameters, including the string tension parameter mu, from fits to cosmological data, and find that in this regard BPS semilocal strings resemble textures more than topological strings. The observed microwave anisotropy at l=10 is reproduced if Gmu = 4.9x10^{-6} (G is Newton's constant). However as with other defects the spectral shape does not match observations, and in models with inflationary perturbations plus semilocal strings the 95% confidence level upper bound is Gmu<1.9x10^{-6} when CMB data, Hubble Key Project and Big Bang Nucleosynthesis data are used (c.f. Gmu<0.7x10^{-6} for cosmic strings). We additionally carry out a Bayesian model comparison of several models with and without defects, showing models with defects are neither conclusively favoured nor disfavoured at present.

    Comments: 15 pages, 13 figures

    Charles Bennet, who points out that it could be a fluke (and inconclusive, needing further checks) was one of the principle investigators of COBE. Also connected with WMAP. One of the top observational cosmologists world wide. It is good the article tapped him for a quote.

    the authors Bevis Hindmarsh etc have been publishing articles as far back as 2004 about seeing statistical evidence of cosmic string in the CMB. I gather that the evidence is model dependent. That is, it says what they suggest only if you make special assumptions. I could be wrong. But we will see how the rest of the community takes this paper. (their earlier work got some citations, but not a lot.)
     
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