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Possible Lorentz violation measured

  1. Jan 5, 2009 #1

    MTd2

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    Lorentz violation bound hugely relaxed.

    Physicists offer foundation for uprooting a hallowed principle of physics
    January 5th, 2009 in Physics / Physics

    Physicists at Indiana University have developed a promising new way to identify a possible abnormality in a fundamental building block of Einstein's theory of relativity known as "Lorentz invariance." If confirmed, the abnormality would disprove the basic tenet that the laws of physics remain the same for any two objects traveling at a constant speed or rotated relative to one another.

    IU distinguished physics professor Alan Kostelecky and graduate student Jay Tasson take on the long-held notion of the exact symmetry promulgated in Einstein's 1905 theory and show in a paper to be published in the Jan. 9 issue of Physical Review Letters that there may be unexpected violations of Lorentz invariance that can be detected in specialized experiments.

    "It is surprising and delightful that comparatively large relativity violations could still be awaiting discovery despite a century of precision testing," said Kostelecky. "Discovering them would be like finding a camel in a haystack instead of a needle."

    If the findings help reveal the first evidence of Lorentz violations, it would prove relativity is not exact. Space-time would not look the same in all directions and there would be measurable relativity violations, however minuscule.

    The violations can be understood as preferred directions in empty space-time caused by a mesh-like vacuum of background fields. These would be separate from the entirety of known particles and forces, which are explained by a theory called the Standard Model that includes Einstein's theory of relativity.

    The background fields are predicted by a generalization of this theory called the Standard Model Extension, developed by Kostelecky to describe all hypothetical relativity violations.

    Hard to detect, each background field offers its own universal standard for determining whether or not an object is moving, or in which direction it is going. If a field interacts with certain particles, then the behavior of those particles changes and can reveal the relativity violations caused by the field. Gravity distorts the fields, and this produces particle behaviors that can reveal otherwise hidden violations.

    The new violations change the gravitational properties of objects depending on their motion and composition. Objects on the Earth are always moving differently in different seasons because the Earth revolves around the Sun, so apples could fall faster in some seasons than others. Also, different objects like apples and oranges may fall differently.

    "No dedicated experiment has yet sought a seasonal variation of the rate of an object's fall in the Earth's gravity," said Kostelecky. "Since Newton's time over 300 years ago, apples have been assumed to fall at the same rate in the summer and the winter."

    Spotting these minute variances is another matter as the differences in rate of fall would be tiny because gravity is a weak force. The new paper catalogues possible experiments that could detect the effects. Among them are ones studying gravitational properties of matter on the Earth and in space.

    The Standard Model Extension predicts that a particle and an antiparticle would interact differently with the background fields, which means matter and antimatter would feel gravity differently. So, an apple and an anti-apple could fall at different rates, too.

    "The gravitational properties of antimatter remain largely unexplored," said Kostelecky. "If an apple and an anti-apple were dropped simultaneously from the leaning Tower of Pisa, nobody knows whether they would hit the ground at the same or different times."

    Animation using Kostelecky's Standard Model Extenstion to predict how apples might fall differently can be viewed at http://www.physics.indiana.edu/~kostelec/movies/agrav3.avi .

    Paper: http://link.aps.org/abstract/PRL/v102/e010402 .

    Source: Indiana University

    http://www.physorg.com/news150388964.html
     
    Last edited: Jan 5, 2009
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  3. Jan 5, 2009 #2

    MTd2

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    This is the article.

    http://arxiv.org/abs/0810.1459

    Prospects for Large Relativity Violations in Matter-Gravity Couplings
    Authors: Alan Kostelecky, Jay Tasson
    (Submitted on 8 Oct 2008)

    Abstract: Deviations from relativity are tightly constrained by numerous experiments. A class of unmeasured and potentially large violations is presented that can be tested in the laboratory only via weak gravity couplings. Specialized highly sensitive experiments could achieve measurements of the corresponding effects. A single constraint of 1 x 10^{-11} GeV is extracted on one combination of the 12 possible effects in ordinary matter. Estimates are provided for attainable sensitivities in existing and future experiments.
     
    Last edited: Jan 5, 2009
  4. Jan 5, 2009 #3

    MTd2

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    It was cited by this article, which tries to relate this with the seasonal decay rate variation of some elements, the proably observed anisiotropy of the orientation of the galaxies and loretz violation.

    http://arxiv.org/abs/0812.2236

    Lorentz Violation and Alpha-Decay
    Authors: Brett Altschul
    (Submitted on 11 Dec 2008)

    Abstract: Relating the effective Lorentz violation coefficients for composite particles to the coefficients for their constituent fields is a challenging problem. We calculate the Lorentz violation coefficients relevant to the dynamics of an alpha-particle in terms of proton and neutron coefficients. The alpha-particle coefficients would lead to anisotropies in the alpha-decays of nuclei, and because the decay process involves quantum tunneling, the effects of any Lorentz violations could be exponentially enhanced.
     
  5. Jan 5, 2009 #4

    marcus

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    Some other animations
    http://www.physics.indiana.edu/~kostelec/mov.html#6

    BTW from what I gather of this, lorentz violation has not been detected. Kostelecky has a framework from which a number of different possible lorentz violations arise, and a number of different experiments are being conducted worldwide to confirm or rule out these different violations.
    He has a good publication track record (over 170 publications) and has been awarded several honors. Seems to be a world-class authority on various types and tests of L.I.V. But unless I'm missing something, no measured violations yet. (Correct me if I'm wrong about that.)
     
    Last edited: Jan 5, 2009
  6. Jan 6, 2009 #5

    marcus

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    Kostelecky just posted a new paper today (6 January)

    http://arxiv.org/abs/0901.0662
    Gravity from spontaneous Lorentz violation
    Alan Kostelecky, Robertus Potting
    51 pages
    (Submitted on 6 Jan 2009)
    "We investigate a class of theories involving a symmetric two-tensor field in Minkowski spacetime with a potential triggering spontaneous violation of Lorentz symmetry. The resulting massless Nambu-Goldstone modes are shown to obey the linearized Einstein equations in a fixed gauge. Imposing self-consistent coupling to the energy-momentum tensor constrains the potential for the Lorentz violation. The nonlinear theory generated from the self-consistent bootstrap is an alternative theory of gravity, containing kinetic and potential terms along with a matter coupling. At energies small compared to the Planck scale, the theory contains general relativity, with the Riemann-spacetime metric constructed as a combination of the two-tensor field and the Minkowski metric. At high energies, the structure of the theory is qualitatively different from general relativity. Observable effects can arise in suitable gravitational experiments."

    I think the press releases and media activity that occurred just prior (5 Jan and earlier) was aptly timed so that it just happened to prepare interest in the 6 January paper:wink:

    We still don't have any indication of a measured Lorentz violation, is that right?
     
  7. Jan 6, 2009 #6

    MTd2

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    No, we don't. But the axis of oportunity is a hint.

    But I also think that the universecould also be a little bit like the Godel univese, that is, it might be that our universe has a non vanishing angular momentum everywhere, intrisic to the space, and that makes the galaxis have a preferable average orientation without having to resort to lorentz invariance breaking.
     
    Last edited: Jan 6, 2009
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