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2012 Gravity essay contest results

  1. May 15, 2012 #1

    marcus

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    http://www.gravityresearchfoundation.org/pdf/abstracts/2012abstracts.pdf [Broken]
    Ted Jacobson got honorable mention with this one
    http://arxiv.org/abs/1204.6349
    Gravitation and vacuum entanglement entropy
    Ted Jacobson
    (Submitted on 28 Apr 2012)
    The vacuum of quantum fields contains correlated fluctuations. When restricted to one side of a surface these have a huge entropy of entanglement that scales with the surface area. If UV physics renders this entropy finite, then a thermodynamic argument implies the existence of gravity. That is, the causal structure of spacetime must be dynamical and governed by the Einstein equation with Newton's constant inversely proportional to the entropy density. Conversely, the existence of gravity makes the entanglement entropy finite. This thermodynamic reasoning is powerful despite the lack of a detailed description of the dynamics at the cutoff scale, but it has its limitations. In particular, we should not expect to understand corrections to Einstein gravity in this way.
    Comments: 9 pages; Essay written for the Gravity Research Foundation 2012 Awards for Essays on Gravitation

    Rovelli teamed up with Aldo Riello and Marios Christodoulou to write an essay that also won honorable mention.
    How to Measure an Anti-Spacetime by Marios Christodoulou, Aldo Riello, Carlo Rovelli, Centre de Physique Théorique, Case 907, Luminy, F-13288 Marseille, EU;
    Abstract – Can a spacetime region with a negative lapse function be detected, in principle? Fermions do not couple to the metric field and require a tetrad field: we show that this implies that a fermion interference effect could detect a negative lapse region, distinguishing “forward evolving” from “backward evolving” spacetimes having a gravitational field described by the same metric.


    Bill Stuckey, Tim McDevitt, and Mike Silberstein won hon. mention with their essay.
    Explaining the Supernova Data without Accelerating Expansion– by W.M.Stuckey1, T.J.McDevitt,2 and M.Silberstein3,
    Abstract – The 2011 Nobel Prize in Physics was awarded “for the discovery of the accelerating expansion of the Universe through observations of distant supernovae”. However, it is not the case that the type 1a supernova data necessitates accelerating expansion. Since we do not have a successful theory of quantum gravity, we should not assume general relativity (GR) will survive unification intact, especially on cosmological scales where tests are scarce. We provide a simple example of how GR cosmology may be modified to produce a decelerating Einstein-de Sitter cosmology model (EdS) that accounts for the Union2 Compilation data as well as the accelerating ΛCDM (EdS plus a cosmological constant).

    Ben Crowell did with his too:
    Tricritical Quantum Point and Inflationary Cosmology by Lawrence B. Crowell, Alpha Institute of Advanced Study 10600 Cibola Lp 311 NW Albuquerque, NM 87114 and 11 Rutafa Street, H-1165 Budapest, Hungary; e-mail: lcrowellATswcpDOTcom
    Abstract – The holographic protection due to inflationary cosmology is a consequence of a quantum tricritical point. In this scenario, a closed spacetime solution transitions into an inflationary de Sitter spacetime. The saturation of the holographic entropy bound is prevented by the phase structure of the system which changes the topology of the early universe.


    Feel free to add other authors, titles and/or links. Time permitting I will, later on today, as well.
     
    Last edited by a moderator: May 6, 2017
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  3. May 15, 2012 #2

    marcus

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    Correction. I confused L. B. Crowell with B. Crowell in the previous post. Different author.

    ===============

    The essay which won 3rd prize in the 2012 GRF contest was posted on Arxiv today:

    http://arxiv.org/abs/1205.3291
    The Unbearable Beingness of Light, Dressing and Undressing Photons in Black Hole Spacetimes
    Timothy J. Hollowood, Graham M. Shore
    (Submitted on 15 May 2012)
    Gravitational tidal forces acting on the virtual e+ e- cloud surrounding a photon endow spacetime with a non-trivial refractive index. This has remarkable properties unique to gravitational theories including superluminal low-frequency propagation, in apparent violation of causality, and amplification of the renormalized photon field, in apparent violation of unitarity. Using the geometry of null congruences and the Penrose limit, we illustrate these phenomena and their resolution by tracing the history of a photon as it falls into the near-singularity region of a black hole.
    8 pages, Essay awarded third prize in the Gravity Research Foundation essay competition 2012
     
  4. May 16, 2012 #3

    atyy

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    B = Ben?
     
  5. May 16, 2012 #4

    marcus

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    Simple error. I misremembered something earlier today, then realized, and fixed it later.
     
    Last edited: May 16, 2012
  6. May 21, 2012 #5

    DrChinese

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    Stuckey is a PF Member and posts here from time to time. :smile:

    Their work is exciting, obviously going against the grain regarding accelerating expansion. Their cosmological model is based on some adjustments due to their quantum model, "Relational Blockworld: A Path Integral Based Interpretation of Quantum Field Theory". This in turn features general agreement to standard QM but has a feature or two that shows up at larger distances/timescales. Worth a look:

    http://arxiv.org/abs/1110.3973
    http://arxiv.org/abs/0908.4348
     
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