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Interesting overveiw

  1. Apr 29, 2004 #1

    wolram

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    interesting overview

    http://www.science.psu.edu/alert/frontiers/AshtekarHandout2-2004.pdf
    Pen state lectures feb 2004 Abhay Ashtekar.


    QUOTE.
    "there was no emergence of the universe from nothing
    because nothing simply does not exist".

    "radiation or matter can transform into geometry and
    vice versa".

    "geometry is physical, it is so similar to matter that it can
    change itself into matter".
     
    Last edited: Apr 29, 2004
  2. jcsd
  3. Apr 29, 2004 #2

    wolram

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    QUOTE.
    yet another consequence that Ashtekar and his colleagues are just
    beginning to explore: the avoidance of the unphysical singularities at the center of black holes, similar to the case of big bang. Possibly even the notorious information paradox can be solved. "In our part of the universe, information which falls into a black hole is lost, but it reappears in a daughter universe," speculates Martin Bojowald. With a smile he adds:
    "However only after it passes through a rather uncomfortable quantum phase at the central bounce.
     
  4. Apr 29, 2004 #3

    wolram

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    QUOTE.
    If one could observe nature with maximum possible enlargement, space and time would dissolve and the granular mesh of the spin network would come to light - or more precisely: the quantum physical superposition of all possible
    configurations of these entities. There is 'nothing' between these graphs. Those entities rest only on themselves, so to speak. "The spin networks do not exist in the space. Their structures produce the space," Smolin stresses. "And they are nothing but abstractly defined relations which
    determine how the edges come together and interlock at the joints ."
     
  5. Apr 29, 2004 #4

    wolram

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    QUOTE.

    Roger Penrose therefore also thinks. "So far string theory does not really agree with the world we see. It requires many complicated assumptions such as extra dimensions and supersymmetry, for which there are no empirical clues, and also provides no definite, univocal prediction for future experiments. All the main problems are unsolved," criticizes Rovelli. "I think it is time to try something else also," he says, advertising for quantum geometry. "Certainly this also has gaps and weaknesses. Like the transition of spin networks to classical spacetime is not yet completely understood, and the calculation of entropy of black holes creates some problems," says Kiefer
     
  6. Apr 29, 2004 #5

    wolram

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    "geometry is physical, it is so similar to matter that it can
    change itself into matter".
    -----------------------------------------------------------------------
    does anyone know how this transformation occurs?

    does LQG support the multiverse theory?

    if something has always existed why do we
    need the BB?

    how can geometry be physical?
     
    Last edited: Apr 29, 2004
  7. Apr 29, 2004 #6

    wolram

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    the presumed Higgs boson that gives them mass. The bosons
    (such as photons and also gravitons), which transmit the subatomic interactions and thus evoke the forces of nature, are encoded in certain excited states of the spin network as changing colors or labels on the graphs.
    -----------------------------------------------------------------------
    does LQG require the higgs boson and the graviton, if not
    why are they included in this description?
     
  8. Apr 29, 2004 #7

    wolram

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    Even time only emerges from the variations of the excited states and the
    links in the networks. In a certain way time is an illusion just as space is. Ashtekar quotes
    Vladimir Nabokov: "Space is a swarming in the eyes, and Time a singing in the ears.
    -----------------------------------------------------------------------
    is time an illusion?
     
  9. Apr 29, 2004 #8

    marcus

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    this article by the science journalist Rudy Vaas does provide
    a broad evocative overview of quantum gravity.

    Sometimes journalism can convey ideas better than technical writing.
    Also popularizations (like Brian Greene "Elegant Universe" and the
    Lee Smolin SciAm article "Atoms of Space and Time") can sometimes getconcepts across more effectively and can be of value to more people.

    It looks to me like what happened is Rudy Vaas wrote this article last year for some magazine similar to SciAm or its German counterpart, and a scientist named Amitaba Sen translated it into English. Then Ashtekar used the English translation as a "hand-out" when he gave a public lecture in February of this year.

    At the moment I cant think of any science journalist covering the QG and string scene who is more knowledgeable, or a better writer, than Vaas. He follows other research efforts besides LQG, by the way. Urs Schreiber reported a conversation with him at a conference this year and was later discussing on the internet another article Vaas wrote "The Duel, Strings versus Loops". Their friendly discussion was on the "String Coffeetable" message board. It seemed clear that Vaas was broad-gauge, not limited to covering one narrow beat.

    but I dont know of any Vaas articles besides the one you found (at Ashtekar's site) and the other one I just mentioned: "The Duel".

    Vaas has impressive talent as a writer and seems exceptionally smart----maybe he is a scientist by training who moved over into popular writing: I dont know his background.
     
    Last edited: Apr 29, 2004
  10. Apr 29, 2004 #9

    marcus

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    evocative science journalism works partly by mental images and
    can raise a lot more questions than it answers
    you have filtered out some questions---a lot actually---
    there are more questions raised here than I can even begin
    to try to answer
    Someone should put Abhay Astekar on the spot to answer some of
    these questions! after all he gave Vaas article as a hand-out at
    his own lecture

    I looked under Vaas name in arxiv and found just the two articles

    http://arxiv.org/physics/0403112
    The Duel: Strings versus Loops
    Ruediger Vaas
    Comments: Extended version from: Ruediger Vaas: Das Duell: Strings gegen Schleifen. Translated by Martin Bojowald and Amitabha Sen. - 10 pages, including 1 table and references
    Subj-class: Popular Physics
    Journal-ref: Bild der Wissenschaft (2004), no. 4, pp. 44-49


    http://arxiv.org/physics/0401128
    Beyond Space And Time
    Ruediger Vaas
    Comments: 7 pages, English translation by Amitabha Sen of the German article "Jenseits von Raum und Zeit" by Ruediger Vaas.
    Subj-class: Popular Physics
    Journal-ref: Bild der Wissenschaft (2003) no. 12, pp. 50-56
     
    Last edited: Apr 29, 2004
  11. Apr 29, 2004 #10

    wolram

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    well Abhay Astekar is at the forefront in this area,
    maybe some of this is just a mind game that has
    reached the public, as you say MARCUS i have
    picked only a few questions that can be asked
    from this article, but is A Astekar or penrose the
    only ones that know the answers, are these few
    so far ahead and willing to publicize such thoughts
     
  12. Apr 29, 2004 #11

    wolram

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  13. Apr 29, 2004 #12

    marcus

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    after saying all the good things one can say about Rudy Vaas
    we still need to be clear about the distinction between popular science journalism and technical or scholarly writing

    popular science writing is to some extent impressionistic
    where technical writing is more careful and reliable
    the good thing about popular writing is that it can suggest directions that
    research might be going, express as-yet-unproven hunches, so one
    gets to know some of the researchers' private thoughts, that they might not venture to say at a conference or have presented in a scholarly journal.

    I'm still reading the article, and re-reading. Find more to think about each time I go back to it. thanks for flagging it.

    I never saw any technical article say that matter could change back and forth with geometry but now it does not seem so impossible:
    states of geometry are represented by labeled graphs

    networks where some of the labels on the links and nodes determine geometric stuff like area and volume

    but matter fields are also described by labeling the graphs too
    so labeled graphs (penrose's spin networks) do provide a plausible framework for geometry to convert back and forth with matter

    perhaps when a star collapses down to a black hole the matter is crushed out of existence and converted to the extreme geometry at the center of the hole--but I have never heard a mechanism proposed for this and I dont know what it could mean to say this---it is way out on the scary edge of speculation.

    so that part of the article: the interchange of matter and geometry, it is too far out for me to contemplate----a shuffling of the labels by some transformation law that I never heard of---a meltdown of the distinction between geometry and matter---no idea what they mean.

    but I do acknowledge that a spin network, or labeled graph, because the links are labeled both with matter fields and geometrical quantities, might provide an arena or a frame for describing this (whatever it means)

    sorry I cant explicate Vaas article better
    it is tantalizing and provocative
     
  14. Apr 29, 2004 #13

    wolram

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    so that part of the article: the interchange of matter and geometry, it is too far out for me to contemplate----a shuffling of the labels by some transformation law that I never heard of---a meltdown of the distinction between geometry and matter---no idea what they mean.
    ---------------------------------------------------------------------------------
    maybe he is thinking the Higgs Field is interchangeable with geometry?
     
  15. Apr 29, 2004 #14

    wolram

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    Last edited: Apr 29, 2004
  16. Apr 29, 2004 #15

    marcus

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  17. Apr 29, 2004 #16
    I think it means that matter must be some submanifold of the overall space-time manifold. How can a single point exhibit characteristics? There are no features "on" a point to calculate. But a manifold, or submanifold, can have properties that are calculable features of the submanifold - global topological features, or frequencies of variations of space-time on the submanifold, etc.
     
  18. Apr 29, 2004 #17

    wolram

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    Originally Posted by wolram
    so that part of the article: the interchange of matter and geometry, it is too far out for me to contemplate----a shuffling of the labels by some transformation law that I never heard of---a meltdown of the distinction between geometry and matter---no idea what they mean.
    ----------------------------------------------------------------------------------
    this was origonally posted by MARCUS.
     
    Last edited: Apr 29, 2004
  19. Apr 29, 2004 #18

    wolram

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    it seems the idea of interchangeability of gravity, mass and energy
    has been around for sometime, but hasn't been taken in to the
    mainstream view, now Baez has bought it into the open by the
    back door, maybe its a good thing to speculate that everything
    has one origin.
    thanks for post MIKE2
     
  20. Apr 29, 2004 #19

    wolram

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    Join Date: Apr 2003
    Location: warwickshire england
    Posts: 849 http://www.nature.com/nsu/991111/991111-3.html

    In 1915, Albert Einstein showed that, in effect, every blob of matter creates a dimple in space-time that diverts the path of a moving particle. The more massive the blob, the deeper the dimple. When one body is accelerated by the gravitational field of another a small fraction of its mass gets converted to energy according to his equation E=mc2, and this is radiated away as 'gravity waves' which spread outwards through space-time
     
  21. Apr 30, 2004 #20

    wolram

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    The energy to separate and polarize the zero energy state was borrowed from the gravitational energy of the Universe. The Universe borrows heavily from its gravitational energy to finance the creation of more matter (Hawking, 1993). Thus, the comparison picture appears as three important equations:
    etc-----.
     
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