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The Trouble with Physics-Woit's review

  1. Aug 28, 2006 #1

    marcus

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    The Trouble with Physics---Woit's review

    Peter Woit has reviewed Lee Smolin's book The Trouble with Physics
    http://www.math.columbia.edu/~woit/wordpress/?p=451

    Also the article in 12 August New Scientist about
    1. emergence of matter in LQG
    2. recovering ordinary gravity---evidence of LQG's correct semiclassical limit
    is available free online:

    http://www.newscientist.com/article/mg19125645.800.html

    The New Scientist article is called You Are Made of Space-time

    Before, it was available only to subscribers. Good article, written by Davide Castelvecchi, a web-editor working for
    the American Institute of Physics (publisher of Physics Today)

    idea that matter arises from braids in geometry.

    twists and tangles that can interact by mutually untieing each other and creating other knots and things like that.
     
    Last edited: Aug 28, 2006
  2. jcsd
  3. Aug 28, 2006 #2
    Thanks Marcus. Very interesting article
    Now to go one step further.
    Quote for the article: "Smolin, Markopoulou and Bilson-Thompson have now confirmed that the braiding of this quantum space-time can produce the lightest particles in the standard model - the electron, the "up" and "down" quarks, the electron neutrino and their antimatter partners".

    If the quantum space-time creates (by braiding) all fundamental particles, then they are all connected, and thus all matter is sitting on the background (quantum space-time). That means that gravity is not an independent force but the observable result of the dynamics of quantum space-time itself. When one braid moves that also influences the position of the other braids.

    Next to that there are other ways how the quantum space-time can create unique combinations, in example not by braiding but by simple penetrations, which create locally multi-layered spots.
     
  4. Aug 28, 2006 #3

    marcus

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    Glad you liked it!

    that same New Scientist link also had a short news item about more evidence that LQG has the right largescale limit---that it does gravity.

    The article is titled Supersizing Quantum Gravity
    (I think "supersizing" means scaling up and looking to see that it matches Newton at large scale)
    ==quote from 12 August NewSci==
    Supersizing quantum gravity

    For loop quantum gravity to succeed as a fundamental theory of gravity, it should at the very least predict that apples fall to Earth. In other words, Newton's law of gravity should naturally arise from it. It is a tall order for a theory that generates space and time from scratch to describe what happens in the everyday world, but Carlo Rovelli at the University of the Mediterranean in Marseille, France, and his team have succeeded in doing just that. "Essentially we have calculated Newton's law starting from a world with no space and no time," he says (www.arxiv.org/abs/gr-qc/0604044).

    Newton's law of gravity describes the attractive force between two masses separated by a given distance. However, it is not so simple to measure this separation when space has a complex quantum architecture of the sort in loop quantum gravity, where it is not even clear what is meant by distance. This has been the biggest obstacle to showing how Newton's law can emerge from quantised space.

    The naive way to measure length in quantised space is to hop from one quantum to another, counting how many steps it takes to reach the final destination. According to loop quantum gravity, however, the fabric of space seethes with quantum fluctuations, so the distance between two points is forever changing, and can even take several values at the same time.

    Working with Eugenio Bianchi of the University of Pisa, Leonardo Modesto of the University of Bologna and Simone Speziale of the Perimeter Institute in Waterloo, Ontario, Rovelli circumvented the problem. The team found a mathematical way of isolating regions of space for long enough to measure the separation between two points. When they zoomed out and used this mathematics to look at space-time on much larger scales, they found that Newton's law popped out of their theory.

    The calculation by Rovelli's team does not yet reproduce the full complexity of Einstein's general relativity, which also describes masses large enough to curve space appreciably. Their result does point in the right direction, however. Lee Smolin of the Perimeter Institute calls it a major step forward. "Their work shows that loop quantum gravity definitely has gravity in it," he says. "It's no longer just pie in the sky.
    "
    ==endquote==
    http://www.newscientist.com/article/mg19125645.800.html
     
    Last edited: Aug 28, 2006
  5. Aug 28, 2006 #4
    I have to wonder what the difference is between permanent particles and virtual pairs. Why is one permanent and the other temporary? Is information lost somewhere else (perhaps behind an horizon) forcing information storage in permanent particles to compensate for the loss?
     
  6. Aug 28, 2006 #5

    marcus

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    I think that Smolin's book would have a case for diversified research strategy even if you don't assume that string is having theoretical problems.

    Giving grad students more exposure to alternative QG approaches, and broader opportunity in what thesis topics they work on (even if as stopgap you have to connect to a different university to get a second advisor.)

    Giving postdocs support to do what they want---based on trackrecord merit of the individual---not bound to a particular research project.

    I think he's got a case regardless of the particular circumstances at present.
    ==============

    Also I would say that the book is going to make background independent non-string QG approaches more visible and this can be purely positive, it does not have to be coupled with string crit.

    You dont have to argue that string looks off tracky or cul-de-sacky just to make the point that some other approaches have gotten exciting lately and will get more notice with things like Smolin's book. It is not exactly teenage turfwar or football. Although that aspect, if not overdone, can add to the entertainment value.

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

    anyway Peter Woit's review naturally (and AFAICS fairly) brings out the string-crit aspect of Smolin's book---and for balance, as soon as I can get the book and read it, I am going to try to highlight the part of the message which is not critical of string but is merely positive to non-string QG.

    the "what comes next" in the title ("The Trouble with Physics: the Rise of String Theory, the Fall of a Science, and What Comes Next")

    what comes next could easily be the kind of 4D "string" theory that some Baez students are investigating. They don't shake and they don't have extra dimensions---it is not string theory in the sense of Witten-Knittin'---but it could be what comes next:smile:

    and so could Freidel and Baratin and Starodubtsev stuff. Or Sundance braids in spinnetworks---the dancing octopods. Laugh at your own risk. Really :smile: All these approaches are manifestly BACKGROUND INDEPENDENT at no point do they require the choice of a geometry.

    Having Smolin's book come out seems likely to open up the picture quite a bit and make all sorts of explicitly background independent approaches more visible---approaches not requiring the preliminary choice of a background metric, that is to say: a geometry---and approaches hospitable to a positive cosmological constant.

    We'll see. In the meantime, I checked the general physics bestseller figures again. As of 10:30 AM eastern on Monday 28 August

    Elegant Universe #3
    TwP #6
    NEW #9
    Road to Reality #10
    Brief History of Time #13
    Warped Passages #18
    Cosmic Landscape #74

    the Kaku books I was tracking earlier were no longer showing in the top 100.

    As of 9:40 AM pacific the next day---Tuesday 29 August

    RtR #1
    EU #3
    TwP #5
    NEW #10
    BHoT #20
    Warped Passages #27
    Cosmic Landscape #39
     
    Last edited: Aug 29, 2006
  7. Aug 29, 2006 #6

    marcus

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    I mentioned Peter Woit's review of Smolin's book in post #1
    I should also give the link to Bee Hossenfelder's review
    http://backreaction.blogspot.com/2006/08/lee-smolins-trouble-with-physics.html

    and her interview with Smolin
    http://backreaction.blogspot.com/2006/08/lees-comments.html

    Peter's review has a lot of substance and quotes from the parts of the book that particularly interested him---mixed with thoughtful reflections of his own. On the other hand I think Bee, in her review, tries to give a balanced overall view of what the book is about. Both are good.
     
  8. Aug 29, 2006 #7

    CarlB

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    Loved the interview with Smolin. Especially the part about hill climbers and valley crossers:

    http://backreaction.blogspot.com/2006/08/lees-comments.html

    My feeling on this is that neither QM nor special / general relativity are currently on the true mountain. If either of them were, then the mountain climbers would have already climbed it. Therefore, both QM and SR must be wrong. Unfortunately, when one states this to almost any physicist, no further conversation can ensue because almost all physicists believe that at least one of these two theories must be correct. And of those, there are a lot of people who believe that both are perfect.

    Carl
     
    Last edited: Aug 29, 2006
  9. Aug 30, 2006 #8

    Chronos

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    I agree. Perhaps neither GR or QT are complete, but still correct at the proper scales. It suggests a third component is missing. It would be interesting to see what remains between GR and QT when reduced to their respective boundaries.
     
  10. Aug 30, 2006 #9

    CarlB

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    My guess is that both GR and QM suffer from the same problem, putting the abstraction cart in front of the reality horse.

    The way the two theories are organized, one begins with very abstract principles (i.e. no preferred reference frames, equivalence principle, Hilbert space, gauge principle). From these one derives the conserved quantities and or symmetries (i.e. energy, charge, angular momentum). From these one derives the equations of motion (i.e. field equations, metric, Dirac equation, perturbation theory). This is exactly backwards, the equations of motion are closer to the structure of the world; "angular momentum" is just a convenient technique for solving a problem.

    I'd rather see both theories derived from a common structure. Like Einstein, I'd expect that the structure would be geometric.

    The only common geometric structure I can see is Clifford algebra or Hestenes' geometric algebra. There are now Clifford algebraic versions of GR that live on "flat" space (the Cambridge geometry group). The simplest wave equation you can write in a Clifford algebra is a generalization of the Dirac equation which makes it a natural basis for quantum mechanics. The existence of flat space gravity suggests that one should assume gravity is a force mediated by a particle on flat space (like all the other forces). This method has such power and speaks so directly to the equations of motion of the two theories that I really don't see why anyone would try to unify QM and GR on any other basis.

    The other abstraction, Hilbert Space, can also be eliminated by using Clifford algebra. Instead of a QM formalism based on spinors or state vectors, one can use density matrices which are very natural in a Clifford algebra. These give a natural geometric interpretation that eliminates such unphysical nonsense as supposing that electrons come back multiplied by -1 when rotated by 2 pi. (That is, the density matrix representation of an electron does no such thing.) Sometimes it seems like I'm the only one who appreciates the density matrix formalism. It got talked about some in this forum: https://www.physicsforums.com/showthread.php?t=124904 , but I really need to write more about it. That discussion was about the problem of defining "A + B" where A and B are states rather than particular state vector representations of states. Since -B is just as good a state vector as B, one cannot easily define linear superposition on the states, just on the representations.

    Carl
     
    Last edited: Aug 30, 2006
  11. Aug 30, 2006 #10

    marcus

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    As of 11:20 AM pacific Wednesday 30 August, standings in the "general physics bestseller" list were

    Trouble with Physics #2
    Not Even Wrong #4
    Warped Passages #9
    Elegant Universe #10
    BHoT #17
    RtR #32
    Cosmic Landscape #43
    Hyperspace: A Scientific Odyssey Through Parallel Universes, Time Warps, and the 10th Dimension #47
    http://www.amazon.com/gp/bestsellers/books/14560/ref=pd_ts_b_nav/102-4540543-7840144

    in the entire physics list (which includes specialized textbooks)
    TwP #3
    NEW #5
    http://www.amazon.com/gp/bestsellers/books/14545/ref=pd_ts_b_ldr/102-4540543-7840144
     
  12. Aug 30, 2006 #11

    selfAdjoint

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    So the ST critique has legs. Sigh! You know I have never been part of this particular Wild Hunt, and I have a very bad feeling about what the upshot of all this is going to be. In a nation where interest in science is more and more a beleagered elite enthusiasm amid the rampant know-nothing populism, this year's science budget was a catastrophe for physics. What do you suppose next year's will be like when congesspersons can wave around copies of NEW to show that the physicists have no idea where they're going, and of TWP to show that they systematically misspend funds allocated to them?
     
  13. Aug 30, 2006 #12

    marcus

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    My advice to the top faculty at the top places is to diversify QG research DAMN fast.

    Get rid of the monopoly WalMart look in fundamental research.

    they should already have done a 10-20 percent diversification into non-string fundamental physics theory.

    To my mind the ONLY seriously damning bit of evidence is that in the whole US there is only a single non-string research GROUP (with more than one faculty member)
    And you can compare that with half a dozen non-string groups abroad.

    And you still hear string apologists saying "we are the one best hope", "we are the only game in town", "our competition does not contact Newtonian gravity" (but see Rovelli's latest), "our competition does not contact QFT" ( but see Freidel)

    If they would stop SOUNDING like they want a monopoly. And if they would act quickly to provide diverse QG options at the top departments, then they could legitmately reply Look, we are doing the best we can!.

    It is that statement which does not ring true under the present circumstances.
     
  14. Aug 30, 2006 #13

    selfAdjoint

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    I will quit this topic after this post. Marcus your response confirms my thoughts. I have often heard the same intransigence in political contexts; "The disasters are not our fault; our foes should have changed their bad ways! We were in the right! It can't be our fault!".

    Many many years ago I read an essay by Hannah Arendt in the New Yorker. It was titled Fiat justitia et ruat respublica. "Do justice though the republic fall" (the original quote has heavens not republic but she changed it deliberately). She concluded that entailing the fall of the republic was a sufficient reason to shrink from pure justice. She was working on her book about revolution then, and perhaps she was thinking of Saint-Just and Robespierre. I was young and hasty at that time and I scorned her thought, but - "Oh, 'tis true, 'tis true!"
     
  15. Aug 30, 2006 #14

    Kea

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    Thank you, selfAdjoint, for some much needed counter levity. How ironic that M-theory should begin to become clear exactly now, amongst such a nauseating outburst of revolutionary rejoicing.
     
    Last edited: Aug 30, 2006
  16. Aug 31, 2006 #15

    selfAdjoint

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    Kea could you maybe start a thread laying out how you see M-theory in the light of modern n-categories or any other innovations you think may have a bearing? Are there any papers on the arxiv about it? Rather than bemoaning the trends perhaps we can start a valid counter-meme?

    Not to be misunderstood; LQG and quantum gravity initiatives as we have seen them explicated here are a wonderful enterprise in physics and I hope and believe the eventual upshot will confirm the work of Thiemann, Rovelli, and all the others. But the insights from the other side are not chopped liver either! Nobody is anywhere near proclaiming victory in the unification stuggle, a struggle, I remind you all, against Einstein's "Old One" the keeper of nature's secrets, not against each other.
     
  17. Aug 31, 2006 #16

    CarlB

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    Also, Kea, eventually I'd like a thread where you explain M-theory in blue-collar worker terms. But not until after I've had a chance to read Smolin and Woit's new books.

    Carl
     
  18. Sep 14, 2006 #17

    ZapperZ

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    Speaking of Woit, read his short interview in Physics World.

    http://physicsweb.org/articles/review/19/9/3/1

    As I've said many times before, eventually they'll discover superconductivity, and Carver Mead's assertion that it is the system that has the clearest manifestation of some of the most fundamental aspect of our universe at the macroscopic scale.

    Zz.
     
  19. Sep 14, 2006 #18
    Yes superconductivity is very interesting.

    Some materials have superconductivity properties, even ballistic conductivity. http://en.wikipedia.org/wiki/Ballistic_conduction . This can be reached i.e. with atomic mono-layers of graphene. http://en.wikipedia.org/wiki/Graphene. Electrodes or wires can be deposited with graphene (sp2) or combined with sp3 (industrial diamond, glassy carbon). sp2 and sp3 combined can make together fullerenes.
    Graphene has some strange properties, like if the electrons follow the mono-layer lattice it's ballistic conductive but if two separate layers are on top of each other they are completely insulated from each other.
    Applications can be i.e. switches for electronics.
     
  20. Sep 14, 2006 #19

    marcus

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    Since this is a thread about Smolin's book---and peoples views and reviews of it---I'd like to know if anyone has an idea of why the book has become a runaway best seller.

    for two weeks, when I pull up the amazon general physics list it is always #1

    and at the present its overall amazon sales rank is 256 compared with the #2 book which has rank 1235.

    what this means is that in this case #1 is not just a little bit out ahead of #2 but it is WAY out ahead. (by a factor of 5 in storewide sales rank)

    The books it is way out ahead of in sales are books by Greene and Hawking and Penrose and Randall and Susskind and Kaku. with some of them it is considerably MORE than a factor of 5.

    So it's probably appropriate to wonder what if anything is different.

    WHAT if anything MAKES THE SMOLIN BOOK SPECIAL?

    I think it is because he doesnt just say that string has failed and hit the wall-----he discusses what comes NEXT. The word NEXT is in the title. He discusses a lot about what comes after.

    I'm curious to know if anybody else who has read all or some of the book has a different take and has found some other angle of why the book is doing well in the market.
     
  21. Sep 15, 2006 #20

    CarlB

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    Well string theory is in trouble and that makes for an audience, but what is truly remarkable about the book is that he tells the story in terms that a non technical audience can understand but without much of the talking down to that you might have seen in recent string theory books.

    I think the book has got real legs. I bought a copy, no, I'm not lending it out. I wrote all over it. And I've influenced at least one person to buy a copy.

    Asking a solid state guy whether solid state has the answers to elementary particles is sort of like asking a librarian if books will help your sex life.

    Carl
     
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