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Welcome to Ilja Schmelzer

  1. Feb 10, 2004 #1

    marcus

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    Ilja Schmelzer, the author of
    http://arxiv.org/gr-qc/0205035
    just introduced himself in one of the Philosophy Forums.
    I am guessing he is a new member of PF
    so I personally wish to welcome him and
    provide an opportunity for anyone who is
    interested in alternative approaches to
    quantizing gravity (besides Loop Quantum Gravity and String)
    to ask Ilja questions.

    It is often said that besides LQG and String
    there are other quantum gravity attempts like
    "condensed matter models" and Alain Connes "noncommutative geometry".
    LQG and String are simply the two main ones.

    However recently in the arxiv's section called "gr-qc"
    (General Relativity and Quantum Cosmology)
    I have noticed numerous "condensed matter" papers, indicating
    that it is an active line of research to try modeling
    gravity by using solid state physics methods. Although
    I know nothing about this, I suppose it must mean having a preferred frame of reference
    and an "aether" giving a kind of substantial existence to
    space. I was under the impression that observation evidence
    had ruled that out! Nevertheless "solid state" approaches to
    gravity are being developed.

    And someone who has written a paper in this line of research
    has appeared here. Ilja's paper is titled:
    "A generalization of the Lorentz ether to gravity with general-relativistic limit"

    here's a link to the thread in Philosophy section
    https://www.physicsforums.com/showthread.php?s=&postid=145184#post145184
     
    Last edited: Feb 10, 2004
  2. jcsd
  3. Feb 10, 2004 #2

    chroot

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    Excellent! Welcome, Ilja, nice to have you here. :smile:

    - Warren
     
  4. Feb 10, 2004 #3
    Fine.

    My approach to quantum gravity is indeed based on
    a preferred frame, or, in other words, on a classical
    Newtonian framework of absolute space and time.

    This space is filled with an ether, and gravity as well
    as matter fields appear as effective fields which describe
    various properties of the ether. The main point of my
    gr-qc/0205035 paper is how relativistic symmetry may be
    derived from simple properties of this ether.

    I want to recommend also a larger paper gr-qc/0001101
    which contains also other considerations, especially
    about Bell´s inequality (I argue the falsification of
    Einstein-causal realism should be simply considered as
    a falsification of Einstein causality: If no realistic
    model without X exists but realistic models with X exist,
    it simply means X is indirectly observed.) and a
    Gedankenexperiment with superposition in quantum gravity
    which has been the starting point for me.

    My current interest is in discrete ("atomic ether")
    models for the standard model fields. This intersects
    with lattice theory - an "atomic ether" model describes
    in some sense a lattice discretization of the continuous
    equations. Thus, I have to meet the problems which appear
    in this domain, escpecially the fermion doubling problem
    and the regularization problem of chiral gauge theory.
    My starting point for a condensed matter interpretation of
    the standard model is hep-th/0209167. The state of the art is
    the inclusion of strong interaction in hep-lat/0311009 which,
    hopefully, may be useful in computations too.

    If you prefer geometric language instead of condensed matter
    interpretation, but also like the ADM decomposition,
    hep-th/0310241 may be of interest.
     
  5. Feb 10, 2004 #4
    I'm going to ask you a question which is not meant to slight you or your ideas in any way and if I do offend I'm very sorry.

    The thing is that with one or two exceptions, the members of this forum who are interested in quantum gravity are really quite unsophisticated. Is your or other non-mainstream approaches the best place for these people to begin? Where would you recommend they start. My feeling is that most enthusiasts really do want to learn about the ideas most representative of current research.
     
  6. Feb 11, 2004 #5

    wolram

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    The thing is that with one or two exceptions, the members of this forum who are interested in quantum gravity are really quite unsophisticated. Is your or other non-mainstream approaches the best place for these people to begin? Where would you recommend they start. My feeling is that most enthusiasts really do want to learn about the ideas most representative of current research.
    --------------------------------------------------------------------
    as a totally ignorant pleb i find the first part of this post
    a bit harsh, maybe the members interested in QG dont know
    everything but then they are not gods.
    as for the second part i enjoy attempting to understand these
    theories and would welcome a gentle introduction to them
     
  7. Feb 11, 2004 #6
    I said "most" not "all", and was simply trying to get some advice from an expert. If you want to see what most people are interested in, just look in scientific american, in which you won't see mention of the kind of work on QG that Schmelzer is doing.
     
    Last edited: Feb 11, 2004
  8. Feb 11, 2004 #7
    Depends on what they want. An enthusiast without professional interest is sufficiently free in his choice. In my humble opinion it should be more interesting to learn something about different approaches (as long as they are not crackpot nonsense) than to learn about the leading approach only. Of course, the number of scientists and publications in a given approach is part of the simple and valuable information which should be given to him. As long as he is unable to judge himself about the advantages of the different approaches, it is the best guess for him to follow the majority, that means, to start with string theory. But then, as a contrast program, it should be quite interesting for him to learn that the good old ether is not as dead as usually believed.

    The question is quite different for a beginner, with own future professional interest. Who is interested in a good job, lots of publications, conferences and so on has to do string theory. Everything else is for people who are not afraid to be outside the mainstream. LQG is here something intermediate, but with the condensed matter approach, especially if you use the e-word (ether), it is very hard to be published and your choice of universities restricted to Third World countries.

    On the other hand, if one is not afraid of this, then the condensed matter approach is the ultimate choice. For a beginner it seems not unreasonable to estimate his future success as the probability of success of the approach / number of scientists already working there. How to estimate the success? That´s the hard part. But the easy part of this estimate is that there is much more competition in the string theory domain. And it is easy to guess that all the easy things are already done.

    The situation is very different in the condensed matter approach. I can give anybody who wants lots of open interesting research questions. Easy math, almost no competition, quite sure that it can be done, and if the approach wins you will be famous. (But nobody pays for it now!)

    Moreover what one has to learn is useful in other domains too. Its possible to switch to condensed matter physics as well as to lattice theory. And there is some probability to find as a side effect something new for these domains: a new useful discretization for lattice gauge theory or a new application of techniques of fundamental physics in condensed matter physics. String theory doesn´t help you in any other domain, except some parts of pure math.

    So much about non-physical recommendations for beginners. Now for the related physical questions, that means the estimate of probability of success of the approach. It seems the best idea to estimate this probability is to look at some easy yes/no questions which are hard to decide and to give each answer a probability 1/2.
    Here are some of these IMHO critical questions:

    - Are there hidden variables for QM?

    Yes => (violation of Bell´s inequality -> Einstein causality falsified -> preferred frame).

    - Is there a preferred frame?

    Yes => equation for the preferred frame necessary, use harmonic coordinates, modify Lagrangian to obtain this => my ether theory.

    - Is Lorentz symmetry fundamental?

    Not => preferred frame the straightforward way to preserve causality.

    - Should we modify GR or QM or above?

    QM => absolute time exists as the parameter in the Schrödinger equation.

    - Rovelli: Relational vs. absolute

    absolute => equation for the absolute background necessary, use harmonic coordinates, modify Lagrangian to obtain this => my ether theory.

    I hope some of these questions will be discussed here in more detail.

    Summary: The condensed matter approach is the optimal choice for beginners who are ready to take the large risc not to follow the mainstream.
     
  9. Feb 11, 2004 #8
    Exactly! jeff has made this point countless times precisely because marcus, who is the most dominant member here, tries to mislead people that really, this isn't important at all and that people who follow string theory are delusional. This is very very wrong.

    I'm trying to learn ST right now, but I guess it's also important not to miss opportunities to learn by asking researchers themselves about their work.
     
  10. Feb 11, 2004 #9

    arivero

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    welcome Ilja

    Hello Ilya; perhaps you could enjoy this non-physics link :-) http://dwardmac.pitzer.edu/Anarchist_Archives/kropotkin/KropotkinCW.html

    That the existence of four elementary particles (fermions) could be related to the dimensionality of space time, is already old speculation. I understand fron te abstracts that you are taking a twist on it, and addressing it only from the point of view of 3D espace.
    Is it working?
    Do you aim to get all the standard model forces induced from gravity principles?
     
  11. Feb 11, 2004 #10

    marcus

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    this brings up the issue of "research demographics"
    e.g. numbers of papers currently being written in different lines
    this picture has been changing
    Here is a recent comparison made with the arXiv search engine

    https://www.physicsforums.com/showthread.php?s=&postid=140715#post140715

    a similar count could be made for condensed matter models of QG if you wish to supply keywords
     
    Last edited: Feb 11, 2004
  12. Feb 11, 2004 #11

    wolram

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    from a bystanders point of view one could write one
    or a million and one papers and prove nothing.
    i dont want to appear rude but haven't we reached
    a stage where experiment is more important than
    writing more papers.
     
  13. Feb 11, 2004 #12
    It would seem obvious that with a universe that is very, very small (near the size of the particles) that speed with respect to the whole is a legitamate concern. How could it not be? Isn't this the same as a "preferred" frame? But in a very large universe, it is not possible to establish velocities with respect to the whole and we can only consider relative speeds, right?
     
  14. Feb 11, 2004 #13
    Re: welcome Ilja

    Thanks.
    Yep, it works. Three generations, eight fermions in each generation and eight real components for each fermion appear as 3 x 2^3 x 2^3.
    2^3 is the dimension of the 3-dimensional external bundle, and the graduation 1 3 3 1 is what we need.
    I aim to get the whole standard model together with gravity from a single universal ether.

    The theory of gravity describes the common properties of a large class of condensed matter theories described by the general axioms
    in gr-qc/0205035. The standard model describes less general, more special properties.
     
  15. Feb 11, 2004 #14
    It's no one's fault that in some areas theory has far outpaced our ability to check ideas experimentally. What would you have us do in the mean time? Further, I think that were always on the look out for some way to generate testable predictions from our theories, whether or not current technology allows them to be checked. We are only human, and we roll with the punches as best we can.
     
    Last edited: Feb 11, 2004
  16. Feb 11, 2004 #15

    wolram

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    It's no one's fault that in some areas theory has far outpaced our ability to check ideas experimentally. What would you have us do in the mean time? Further, I think that were always on the look out for some way to generate testable predictions from our theories, whether or not current technology allows them to be checked. We are only human, and we roll with the punches as best we can.
    -------------------------------------------------------------------
    of course your only human and no doubt at the leading
    edge, but would you be kind and give an overview of
    testability of the different theories.
     
  17. Feb 11, 2004 #16
    My ether theory of gravity predicts a globally flat universe.
    Some qualitative differences to GR (testable in principle but not in reality): The "frozen stars" which replace black holes do not Hawking radiate. Incoming neutrinos will come out later. There are two free parameters to fit "dark energy".

    My approach to an ether interpretation of the standard model predicts the number and basic structural properties of the
    SM fermions.
     
  18. Feb 11, 2004 #17

    wolram

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    My ether theory of gravity predicts a globally flat universe.
    Some qualitative differences to GR (testable in principle but not in reality): The "frozen stars" which replace black holes do not Hawking radiate. Incoming neutrinos will come out later. There are two free parameters to fit "dark energy
    ---------------------------------------------------------------------
    i cant speak for anyone other than myself, but i think your
    theory to replace BHs with frozen stars is a good starting
    point, given that there is already a wealth of information
    already available, i will be indebted to you if your initial
    responses are understandable to the majority.
     
  19. Feb 11, 2004 #18
    I'm definitely not at the leading edge of anything. Right now I'm just struggling to understand basic string theory and will likely not be in a position to say anything except in the broadest terms for quite a while. To the best of my knowledge though, no testable (or maybe any) predictions have been extracted from string theory yet, but like I said, I'm just a beginner.

    I'm pretty sure though that if theorists all quit, there wouldn't be much to talk about here at PF. :smile:
     
  20. Feb 12, 2004 #19

    arivero

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    From the papers, structural properties seems an exagerated claim.

    In a first reading it is not clear how the elements of each stage in the graduation map into the components of fermions.

    But, even if it were clear, the main worry is that you do not seem to find any limitation when doing the association. One should expect that the different masses and CKM mixings appear as a consequence. Furthermore, the physical properties of the leptonic sector are very different from the quark sector, and your papers aim to a wholly symmetric construction.

    Finally, but this is a minor problem the recipe is not clearly stated, just it is pointed out. From a first study of the work, I do not get how many fermions, particles, antiparticles and generations should I get if I same the same play in one espatial dimension (1+1 QFT), two, or three.

    You need to get restrictions if it is going to be a sensible theory. There are four fundamental masses in each generation, and such thing should appear somewhere.
     
  21. Feb 12, 2004 #20
    Do you think so? My approach gives 192 degrees of freedom, the same as the 24 fermions of the standard model. There would be many ways to obtain the same number 192. I obtain the number 192 as
    T x /\ x /\, means, as 3 x 8 x 8, as in the standard model. In /\ we have a degree of a differential form, which gives an additional structure named graduation (1,3,3,1). We have a similar graduation by electromagnetic charge in the standard model. We also have electroweak pair structure in the standard model, and the Hodge star operator in /\. This is not only a pure coincidence in the number of degrees of freedom, but already a lot of nontrivial structure.

    Is there anything comparable from string theory?
    For the fermion components the (1,3,3,1) graduation seems not important.
    At the current moment I have not much ideas about the masses. My main worry for me is lattice theory for electroweak interaction.
    Which differences do you have in mind? Of course, the strong interaction acts in a very different way on quarks and leptons. The unique scheme for this action is described in hep-lat/0311009.
    The geometric interpretation is given in hep-th/0310241 as
    T x /\ x /\ with the exterior bundle /\. Here the tangential bundle T gives the number of generations, the first /\ a generation, and the second /\ a single fermion.
    Of course it would be nice to get restrictions for the mass terms. But I don´t expect a parameter-free final theory which allows to derive all masses. Last not least, if there really is something like a crystallic ether, there will be some free material parameters of this ether. Nonetheless, it seems reasonable to hope for an explanation of some regularities.
     
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