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Shining light thru the sun: evidence of axions?

  1. May 27, 2007 #1


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    this just appeared in the peer-review journal Physical Review Letters. I noticed the preprint of it on arxiv last year and thought it was pretty far out. Here is the revised October 2006 preprint:

    Shining light through the Sun
    Malcolm Fairbairn, Timur Rashba, Sergey Troitsky
    Published in PRL under title "Transparency of the Sun to gamma rays due to axionlike particles"
    (Submitted on 30 Oct 2006 (v1), last revised 19 May 2007 (this version, v2))

    "It is shown that the Sun can become partially transparent to high energy photons in the presence of a pseudo-scalar. In particular, if the axion interpretation of the PVLAS result were true then up to 2% of GeV energy gamma rays might pass through the Sun, while an even stronger effect is expected for some axion parameters. We discuss the possibilities of observing this effect. Present data are limited to the observation of the solar occultation of 3C 279 by EGRET in 1991; 98% C.L. detection of a non-zero flux of gamma rays passing through the Sun is not yet conclusive. Since the same occultation happens every October, future experiments, e.g. GLAST, are expected to have better sensitivity."

    The relevance for us in Cosmo forum is that AXIONS if they can be proven to exist MIGHT BE DARK MATTER
    and this quasar eclipse experiment is a TACTIC FOR SEEING IF AXIONS ARE REAL. People are getting clever about ways to get evidence of the existence of dark matter, if it exists. I think it's exciting.

    The PhysWeb news site picked up on the story and had this to say:

    "Quasar eclipses could clarify axion mystery
    Physicists have devised an experiment that could clarify whether hypothetical ultralight particles called axions -- which some claimed were glimpsed in the lab last year -- exist for real. It involves using space telescopes to check whether gamma rays from a quasar billions of light years away can travel through the Sun by interacting with its magnetic field (Phys. Rev. Lett. 98 201801)."

    PhysWeb requires a subscription, but here is an alternative source
    called SciCentral.
    Last edited: May 27, 2007
  2. jcsd
  3. Jul 6, 2007 #2


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    Axions ruled out by PVLAS There go the axions.....
  4. Jul 6, 2007 #3


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    Personally I've never been a fan of axions, but Frank Wilczek speaks well of them :smile:

    As I read the PVLAS announcement they did not actually RULE OUT the existence of axions.

    They simply RETRACTED some supporting evidence. A few months back they interpreted some data as positive indication, and they now rescind that interpretation.

    For better or worse, axions have not been ruled out, they just have not been seen yet. And people go on looking for them.


    just as a side-comment, when it comes to big questions like about inflation dark energy dark matter conditions prior to big bang...
    when it comes to big questions, I expect more progress in Quantum Gravity than I do in Particle Physics.

    Bojowald just conjectured a rather interesting explanation of acceleration just using the ingedients of LQG. His proposed explanation would make a "dark energy" field unnecessary. And he has ideas of how to test it.

    I think that by looking at the fundamental degrees of freedom that underly space time and matter, people stand a better chance of coming up with new insights than they do by going over and over the same particle theory ground (with its basis in an old idea of spacetime).

    You get to a point where finding a new particle doesn't help, and going out looking for a new particle is not the best way to address the main questions.

    But all the same good luck to them in their hunt for axions.
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