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Urs Schneider's allegations about the Ashtekar Shadow states paper

  1. Feb 28, 2004 #1

    marcus

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    Urs Schreiber's allegations about the Ashtekar "Shadow states" paper

    Urs has made serious allegations about the paper
    "Quantum gravity, shadow states, and quantum mechanics"
    by Abhay Ashtekar, Stephen Fairhurst, and Joshua Willis.

    However I've not seen any place where he openly refers to the paper by title and named the authors! So I guess there have been vague hints and rumors and suggestions flying around, with no obvious attachment to substance. Several people besides myself seem to have been confused about what was being discussed.

    I saw a stray reference to a license plate (gr-qc/0207106) and mistook it for some other 2002 paper, in the absence of identifying context, and Urs corrected me and said it was by Ashtekar. So then I knew. I dont ordinarily recognize papers by their arxiv numbers or my friend's cars by their license plates:smile:

    Anyway, when you have serious criticisms of a particular paper, then, as Urs would doubtless be the first to point out, it is good scholarly practice to be open and explicit and public about it. So I have started a Ashtekar "Shadow states" thread and I hope Urs will post there and say exactly what he thinks is wrong or dubious about the paper.

    Criticism is often extremely valuable and useful. My personal estimation of Urs is very high. I have the highest regard for his intelligence and expertise. Also a high regard for Ashtekar--who rates a thread of his own instead of being hidden in some closet of a Thomas Thiemann thread.

    So I think it will most probably be very helpful to have all of Urs objections to this paper to be made clear and out in the open.

    There is a particular reason why I think this could be especially interesting to see in the present, which I will explain in the next post.
     
    Last edited: Feb 28, 2004
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  3. Feb 28, 2004 #2

    marcus

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    why it would be especially interesting

    Urs,
    One reason I think it would be helpful to have you spell out your criticisms is that currently there are several different approaches being tried to connect with the low energy limit in LQG.

    Ashtekar et al's paper is one of these initiatives. When a number of different tentative attempts are being made criticism can help to eliminate the less-promising ones and the false starts.

    Indeed I was under the impression that this paper had followed a blind alley, but someone corrected me about this. I had that impression first because it does not look and feel like the LQG I'm used to: didn't seem to be typical Loop Gravity----and second because it has gotten almost no citations compared with what major Ashtekar papers usually get. But those were just impressions, not based on anything solid. Another poster here (who I believe knows more than I do) has told me the paper is relevant to LQG!

    So here we have an important research area (the different avenues people are exploring to connect with physics at low energy) and a paper that is potentially important (in at least one knowledgeable person's view) and you have made analysis that apparently casts doubt on it. Something "odd" or "weird" or "non-standard" or "drastically different" I seem to recall.

    Though I think you said you found no flaw in the mathematics per se.

    Hope I am not misquoting your objections to the paper. I, and maybe others besides myself, would be happy if you would discuss this in the regular way, in a thread explicitly devoted to this particular paper.
     
  4. Feb 28, 2004 #3
    Give him a break

    Hi Marcus,

    In Urs' defense, I happen to know that he will be away for the next three days enjoying a nice internet-free vacation on the beach.

    I think that instead of insinuating that Urs is being somehow academically underhanded by not provided you the references AGAIN you should be down on your hands and knees thanking him for his patience to even talk to you. He went through a LOT of trouble to find those page numbers and references in Rovelli's book for you the first time. I specifically remember him telling you, but I can't seem to find them again either. Now you want him to dig through Rovelli's book AGAIN to find those SAME equations and page numbers that he already went to the trouble of finding for you himself. He is extremely busy with his OWN research. In case you didn't know, graduate school in physics is not a stroll in the park. I hope he enjoys his much needed break away from studies.

    This is some appreciation you show.

    Best regards,
    Eric
     
  5. Feb 28, 2004 #4
    i think his last name is Schreiber, not Schneider
     
  6. Feb 28, 2004 #5

    marcus

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    thanks, I corrected the spelling to Schreiber in the post
    but it takes a mentor to correct the spelling on the menu
    hope someone does!
     
  7. Feb 28, 2004 #6

    marcus

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    Re: Give him a break

    That is great. I think he's a nice person too. Hope he enjoys the break.

    Eric,

    that is not what I am asking here
    this is about a paper by Ashtekar et al
    that Urs says he has discussed at length

    Urs says: "Since I have mentioned this paper for quite a while now and many times, here, on s.p.r. and at the Coffee Table, have written summaries and critical discussions of this paper in these three groups, have compared its techniques to those used by Thomas Thiemann,..."

    https://www.physicsforums.com/showthread.php?s=&postid=153331#post153331

    I cant find his discussion in the Thiemann thread
    or any place where it is made explicit what paper he's talking about
    I would like it to be in a place we can find it
    with the name of the paper being discussed
    so its clear what is being talked about

    Do you have any links to discussion of this paper?

    Sorry if I seem demanding but Ashtekar is an important
    person---one of the founders of the field---and critical
    discussion of one of his papers really needs its own thread.
    I dont want to argue with Urs claims! I dont want them buried
    somewhere in the TT thread or on some other board.
    So far all I see is conclusion-words like "weird" "drastically different" "not honest" (meaning not genuine).

    If work by these authors (Ashtekar, Willis, Fairhurst) is being
    put on trial and judged dubious or off-beat or inconsistent with commonsense or whatever (I dont know exactly what the accusations amount to), it needs to be out in the open.
     
    Last edited: Feb 28, 2004
  8. Feb 28, 2004 #7

    marcus

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    another Urs comment on Ashtekar et al

    I found another place where Urs was talking about the
    Ashtekar/Fairhurst/Willis paper, but the title of the paper was no where in sight. And none of the authors were mentioned.
    there was just the arxiv code--the gr-qc number 0207106

    https://www.physicsforums.com/showthread.php?s=&postid=153289#post153289

    Now the great thing is this: not only is Urs obviously a nice, fairminded, and intelligent person but he could also be correct in his assessment of Ashtekar/Fairhurst/Willis's paper.
    It could be that the paper is drastically (as Urs says) speculative and even dangerously abnormal. We only need to make this claim clearly and openly and clear so people can worry about that if they want. Here is what he was saying on that occasion about

    "Quantum gravity, shadow states, and quantum mechanics"
    by Ashtekar, Fairhurst, Willis
    http://arxiv.org/gr-qc/0207106

    ---------quote from Urs post----
    And let me emphasize that by 'highly speculative' I mean something drastic. Of course every theory of quantum gravity in the absence of experiments has to be speculative. In string theory there is the single and obvious speculation that strings exist. Everything else follows. If they don't exist, they don't. Fine.

    But in LQG the speculation is that at the Planck scale the quantum principle itself is radically different from everything we know so far. Maybe one can argue that the modified priciple should still be called 'canonical'. Words are arbitrary. But it still refers to a concept drastically different from what is usually called canonical, outside the LQG-literature. You wouldn't claim that the LQG-like quantization of the 1d nonrelativistic particle in gr-qc/0207106 is 'canonical' would you? It's not canonical - it's weird!

    I can say that with full confidence because if we know one thing for sure it is how the quantum theory of the 1d nonrel particle works. And it works very differently from the supposedly 'canonical' theory that is presented in gr-qc/0207106....
    --------end quote---------
     
    Last edited: Feb 28, 2004
  9. Feb 28, 2004 #8

    selfAdjoint

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    Marcus, Urs discusses the shadow states paper, with the title and the authors' names, plus a link, at this permalink on the Coffee Table site. As he said, he also discussed it at s.p.r., but that was just a summary of his discussion on the Coffee Table. It has page numbers and all.
     
  10. Feb 28, 2004 #9

    marcus

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    Great! Thanks. I will immediately paste it in here. I was put off when he refused to give me a link like that. Probably many here have already read this, but for the convenience of any new visitors, and my own (since I would have to modify my software to make Coffee Table legible), here it is:

    Too bad the math symbols don't copy and paste. Nor did the copy and paste work on the last line of text! Thanks to Jeff supplying them I have edited in the missing part of the last sentence.
     
    Last edited: Feb 28, 2004
  11. Feb 28, 2004 #10

    jeff

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    You know what put's me off marcus? That you omitted the final few words, and since they were really the crucial part, it's impossible not to see that you did this on purpose to mislead. Here's the rest of the quote:

    "his approach however has very little in common with what one usually calls ‘quantization’. And it is also doubtful that an argument as in Ashtekar,Fairhurst&Willis can recover the usual theory in this case, I think."

    As I pointed out in another thread, I don't just "think", I know.
     
  12. Feb 28, 2004 #11

    selfAdjoint

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    Translation, the special argument in the shadow states paper wil not extend to broad LQG. Probably not (I don't "know" that, but then I don't "know" very much). So what? If you are just cautioning into reading too much into the paper, consider me cautioned.
     
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