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Featured A Erik Verlinde's new view on dark matter

  1. Nov 10, 2016 #21

    Berlin

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    New paper today in PRL of S.S. McGaugh et al (see http://physics.aps.org/) which looks like support for Verlinde. Verlinde also citates earlier papers from these people. They say that only accelaration is the relevant parameter, just like it seems with Verlinde. Dark matter is locally coupled to baryonic matter, if I understand it right. Needs more study though!

    See also their arxiv: https://arxiv.org/pdf/1610.08981.pdf

    berlin
     
    Last edited: Nov 10, 2016
  2. Nov 14, 2016 #22

    haushofer

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    I think I would become more convinced if his theory can explain the Bullet Cluster. Still have to read the full paper though, I'm first trying to understand the developments leading to these ideas.
     
  3. Nov 15, 2016 #23
    This quote from the paper mentions quantum information which is evenly divided over all tensors in the network. Does anyone have some reference or paper which explains to me how this information becomes evenly divided? Is this purely the timescale or is there more to it? How does this information propagate through the network? Like in the case entanglement is lost due to observation.
    And I am assuming this network actually is the entire universe, is this correct?
     
  4. Nov 15, 2016 #24

    MTd2

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    I think I can give a wave hand explanation On section 7.1, he gives the answer where dark matter is similar to elastic memory (I think a better analogy is a deformed plastic). In the bullet cluster, dark matter is ahead of the collisional gas. Since the elastic mass is really similar to a sort of rubber surface attached to a galaxy, where all its mass comes from tension, it will "detach" from each cluster of baryon mass, and accelerate faster towards each other.
     
  5. Nov 15, 2016 #25
    How can i understand his view as a 1st year physics student with no background in most of the topics discussed.
     
  6. Nov 16, 2016 #26

    martinbn

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    Try to read the paper.
     
  7. Nov 16, 2016 #27

    haushofer

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    Thanks. I have to think about it still though.
     
  8. Nov 16, 2016 #28
  9. Nov 17, 2016 #29

    ohwilleke

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    Or not. Additional dark matter is needed in clusters for MOND and its relativistic extension TeVeS, but that is not the only modified gravity game in town, and I do not believe that TeVeS need dark energy as it, like general relativity, has a cosmological constant (which is a gravity modification) in lieu of a dark energy substance, that captures the observed acceleration of the expansion of the universe.

    - J. W. Moffat and M. H. Zhoolideh Haghighi, "Modified gravity (MOG) can fit the acceleration data for the cluster Abell 1689" (16 Nov 2016).

    The introduction of this short paper observes that:

    The conclusion of the paper notes:

     
    Last edited: Nov 17, 2016
  10. Nov 17, 2016 #30

    haushofer

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    Just curious: a lot of these approaches rely on weak field approximations. Could it be that because of that we're overlooking non-linear effects which could explain the data? I'm thinking in the spirit of e.g. monster/rogue-waves, caused by non-linear effects of the hydrodynamical equations underlying them.

    Probably too naive, but just wondering :)
     
  11. Nov 18, 2016 #31

    ohwilleke

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    I think that it is highly likely that there are non-linear effects in weak fields that are giving rise to phenomena interpreted as modified gravity or dark matter, and that some of the non-linearities get ignored inappropriately because of simplifying assumptions that aren't justified or a failure to recognize how a very slight effect can have a cumulatively important consequence in large scale systems when a force is always attractive.
     
  12. Nov 18, 2016 #32

    PeterDonis

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    Do you have any references for this type of model being applied in cosmology?

    Based on what theoretical model?

    Everyone, please bear in mind the PF rules about personal speculations.
     
  13. Nov 20, 2016 #33

    ohwilleke

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    A summary of some of the empirical data can be found, for instance, at Federico Lelli, et al., "One Law To Rule Them All: The Radial Acceleration Relation of Galaxies" (October 27, 2016). Examples models addressing this data or exploring non-linear extensions of GR include: J.W. Moffat and M.H. Zhoolideh Haghighi, "Modified gravity (MOG can fit the acceleration data for the cluster Abell 1689" (November 16, 2016); Borut Bajc and Francesco Sannino, "Asymptotically Safe Grand Unification" (October 30, 2016); Sascha Trippe, "Can Massive Gravity Explain the Mass Discrepancy - Acceleration Relation of Disk Galaxies?" (May 28, 2013); Sacha Trippe "A Derivation of Modified Newtonian Dynamics" (March 28, 2013) (using a massive graviton approach); Dagoberto Escobar, "Born-Infeld type modification of the gravity" (September 28, 2012, last revised November 5, 2012); Max I. Fomitchev, "Dark Matter and Dark Energy as Effects of Quantum Gravity" (September 7, 2010); M. Wellmann, "Gravity as the Spin-2 Quantum Gauge Theory" (March 6, 2001); Leonardo Modesto, "Tree Level Gravity - Scalar Matter interactions in Analogy with Fermi Theory of Weak Interactions using Only a Massive Vector Field"(January 4, 2004).
     
  14. Nov 20, 2016 #34

    haushofer

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    All I'm saying is that when one applies the linear approximation, non-linear effects could possible give rise to phenomena one cannot account for without doing a full numerical analysis.

    I don't see how remarks like this contradict PF rules.
     
  15. Nov 20, 2016 #35

    haushofer

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    I was asked to give a 1-hour talk about it at my university for future physics teachers; in Holland, where I work, it was quite a media hype. Maybe I could turn the talk into an insight later on. Details are still not clear to me, which is not strange of course, but it is also nice to put the story into a historical context. E.g. regarding the question about Dark Matter whether the theory is incomplete, or the observation. As Carroll says, the first one is much cooler and more interesting for the media to speculate upon :P
     
  16. Nov 21, 2016 #36

    ohwilleke

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    Another new paper supporting the importance of non-linear quantum gravity effects in weak fields.*

    A. Deur, "Self-interacting scalar fields in their strong regime" (November 17, 2016).

    * Deur's reference to the strong field regime in gravity is to fields generated by large masses, not to large gravitational forces. Usually a weak gravitational force generated by a large mass would be called the weak field regime, while the term of "strong field" regime in gravity would be limited to cases where the strength of the gravitational field in absolute terms was very large at a given point (e.g. near black holes).

    This paper builds on previous papers (both published in peer reviewed journals) in 2009 and in 2014.

    What Deur does in all three papers is to overcome the mathematical difficulties involved in analytically solving a full self-interacting spin-2 graviton equation by modeling a self-interacting spin-0 graviton which captures the physics of the static case. He then convincingly argues that his conclusions (suggested by a scalar simplification of QCD which is matched in full spin-1 gluon QCD) would not be eliminated by generalizing his self-interacting spin-0 graviton model to the spin-2 case, because in the systems studied, the tensor contributions of angular momentum, linear momentum, pressure and electromagnetic flux that are present there are modest compared to the self-interaction effects observed in the spin-0 case.

    (Newtonian gravity is a non-self-interacting spin-0 graviton model except that the non-interacting spin-0 graviton couples to energy (including photons) as well as to rest mass and propagates at the speed of light rather than instantaneously.)

    Both Deur's work and the MOG papers by Moffat refute the claim of Clowe, et al. in their 2006 paper that: "An 8-sigma significance spatial offset of the center of the total mass from the center of the baryonic mass peaks cannot be explained with an alteration of the gravitational force law, and thus proves that the majority of the matter in the system is unseen."
     
    Last edited: Nov 21, 2016
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