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Will LQG explain the constants?

  1. Apr 9, 2005 #1

    marcus

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    the values of some of the fundamental numerical constants occurring in the standard models of matter and cosmology are considered to be favorable to life and people wonder why they are what they are

    for example the finestructure constant alpha, why is it around 1/137?

    for example the cosmological constant Lambda, why is it around E-120?

    (the currently estimated value in rationalized Planck units is 0.85E-120)

    A WAY HAS BEEN SUGGESTED by which LQG could explain some of these basic constants without appealing to the existence of life (which is unfalsifiable and thus not a scientific theory: it indiscriminately "predicts" anything we could possibly observe and any experimental outcome we could measure).

    The model for explaining basic constants, called CNS by Lee Smolin, is FALSIFIABLE, in the sense that it predicts quantitative outcomes of observations which conceivably could go againt it and prove it wrong. So it has some definite predictive value----it UNpredicts certain outcomes of future experiment.

    What Motl has called "The Anthropic Lack of Principles" does not unpredict anything. It does not bet its life on the outcome of some future measurement and risk empirical disproof. Instead, it can accomodate any future observation. Therefore by the traditional standards of empiricism it is meaningless.

    However the CNS principle achieves similar explanatory aims and is falsifiable. CNS has predictive content in the sense that it unpredicts certain things, which might be observed next year or tomorrow or whenever.

    CNS stands for "cosmic natural selection" but it could also be thought of as signifying "constants natural selection". It proposes an evolutionary mechanism which selects for "good" values of the basic constants.

    In this case "good" means favoring REPRODUCTIVE SUCCESS analogous to what drives darwinian natural selection processes in other contexts.
     
    Last edited: Apr 9, 2005
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  3. Apr 9, 2005 #2

    marcus

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    the CNS principle is based on the premise that the formation of a black hole reproduces the universe
    (with some variation of physical constants analogous to genetic mutation)

    so values of the basic constants (like alpha and Lambda) which promote the plentiful production of black holes contribute to the REPRODUCTIVE FITNESS of the universe and to its reproductive success.

    this leads to experimental checks and tests of the same sort as one may apply to biological natural selection.

    in particular Smolin derives from the CNS principle an upper bound of around 3 solar masses on the size of a neutron star. (I dont recollect the exact number maybe it is 2.5 solar masses.)

    If tomorrow some astronomers observe a pulsar (a type of neutron star) which belongs to a binary pair allowing reliable determination of the mass, and the mass of this pulsar turns out to exceed Smolin's CNS upper bound then CNS is shot down. It is able to predict something that might not be observed.

    there is more to it, and I am oversimplifying, but that is the main thrust
    there is more in
    "Scientific Alternatives to the Anthropic Principle"
    http://arxiv.org/hep-th/0407213
     
    Last edited: Apr 9, 2005
  4. Apr 9, 2005 #3

    marcus

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    the reason having alpha be around 1/137 contributes to reproduction is that it allows a large number of stable chemical elements to exist (a big periodic table with a rich chemistry) without which

    clouds of dust and gas which are ready to condense down to form stars would be less able to radiate away surplus heat. any kind of condensation requires dumping heat---usually accomplished by radiating it off into space

    in other words, the existence of carbon and oxygen speeds up the condensation of stars

    if the only elements were hydrogen and helium then maybe there could be some stars, but they would not form so readily

    and fewer stars eventually means fewer black holes, so fewer offspring

    so if a cosmos has a bad alpha, that only lets it have two chemical elements (hydrogen and helium), then it wont have as many children to pass along its bad alpha to.

    but if a cosmos has a good alpha then (other things being equal) it will have a lot of stars and black holes and it will have a lot of children to inherit its good alpha.
     
    Last edited: Apr 9, 2005
  5. Apr 9, 2005 #4

    marcus

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    the role of LQG here is that it permits a theoretical probing of the major singularities of Gen Rel, to see if it is theoretically possible that
    the formation of a black hole reproduces the universe

    you can read more about this in Smolin's essay
    "Scientific Alternatives to the Anthropic Principle"

    Basically the Bang and Hole singularities have to be cured by an improved Gen Rel (a quantized version) which is what LQG tries to be. and then conditions where the singularities used to be have to be studied, to see if hole leads to bang.

    this is an unfamiliar and even (for some people I imagine) unsettling prospect, it may reveal violations of accepted physical laws, or limitations on their applicability. To put it simply, we have to take our physics thru what was once a singularity. Physical constants may not remain perfectly constant in those abnormal circumstances, and the laws of thermodynamics may balk, and all that.

    so the business of hole leading to bang needs to be approached gingerly with a great deal of caution on the part of theorists.
     
    Last edited: Apr 9, 2005
  6. Apr 9, 2005 #5

    wolram

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    By Marcus.


    this is an unfamiliar and even (for some people I imagine) scary prospect, it may reveal violations, or limitations of applicability, of accepted physical laws that work in more usual context. basically we have to take our physics thru what was until recently a singularity. physical constants may not remain perfectly constant in those abnormal circumstances, and the laws of thermodynamics may balk, and all that.

    This does not worry me, as it may have been a unique event, as long as
    it predicts what is in our universe, what is the problem?
    It goes beyond the grain to think that a theory like this is correct, but
    why not, what we have now is a mishmash of splinted theories that go
    nowhere, so any explanation is welcome
     
  7. Apr 9, 2005 #6

    marcus

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    I should qualify what I said, and make clear my reservations, so that no one expects too much of the CNS principle.

    1. it may be proven wrong. even as we speak some astronomer may be measuring the mass of a neutron star which is more massive than Smolin's limit. or someone maybe be observing something else which contradicts the notion that cosmic evolution optimizes the constants for BH production.

    2. it needs a lot more work. there are several dozen basic constants (in standard model physics and cosmology). Which of them bear on black hole formation? If they were optimized for BH production, then what would their values likely be? Are the observed values close to the measured ones, or not? Not all the theoretical work has been done.

    3. it involves judging what is reasonable odds. Like we can believe that gazelles were selected for speed, because you examine details of the animal and they look optimized, within a few percent of what it ought to be if the aim was to make the animal fast. If you come across something that doesnt fit, well maybe it just hasnt evolved good YET. But since most stuff looks optimized at least within reasonable tolerances, the idea that it evolved for speed is PLAUSIBLE.

    To sum it up, the CNS could be shot down observationally today or tomorrow. Or LQG might fail to show that hole and bang conditions are theoretically compatible, leaving doubt as to how hole could CONNECT to bang.

    Or when they look carefully at all the physics constants they might find one that is NOT evolved for hole production. As if when you examine gazelles closely you were to discover that each animal has a 5 pound left toenail----something obviously interfering with speed.

    And then there is the business that part of the argument depends on judging how close to ideal optimum you are going to say is optimized. Suppose one of our constants turns out to be within 5 percent of perfect (for making holes) but not to be within 1 percent. What do you say? Do you say that it was on its way to evolving towards the optimum but hadnt yet been thru ENOUGH ITERATIONS?

    So I am not discussing some neatly tied, trim package. the idea is still in the works. (and it risks falsification, like any good idea should). But I will say frankly that NONE OF THESE RESERVATIONS that I've stated worries me in the slightest.
     
    Last edited: Apr 9, 2005
  8. Apr 9, 2005 #7

    wolram

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    LQG, seems to be a possible melting pot for trial and error, out of the
    multitude of events, one came about that allowed our existence, but
    that is not science its more philosophy.
    LQG seems to be the only candidate that may unlock the DNA of the
    universe to date, i doubt it will be the final answer, but i will bet it will
    be something similar that takes its place.
     
  9. Apr 9, 2005 #8

    marcus

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    outside, our young apple tree is covered with white blossoms
    and the bees are taking care of scrambling its genes, which was the idea
    of evolving flowers in the first place.
    While outside enjoying the sun for a while, I thought of something by William Yeats the poet:

    IN GRATITUDE FOR UNKNOWN INSTRUCTORS

    what they undertook to do
    they brought to pass.
    all things hang like a drop of dew
    upon a blade of grass.
     
  10. Apr 9, 2005 #9

    wolram

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    Marcus i live but a few miles from where the bard once lived, local legend
    says that he was a drunken, but who care his words are forever.
     
    Last edited: Apr 9, 2005
  11. Apr 9, 2005 #10

    Chronos

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    I tend to doubt we can derive all the fundamental physical constants from first principles. We may, however, be able to explain the relationships - i.e., dimensionless numbers like alpha. I was doing some casual surfing on this and came up with some pretty weird stuff. While checking NIST I noticed the show the value of alpha being derived from the 'Wales constant' instead of the expected [by me] e^2/hc. I did some checking on this Wales constant thing, still expecting to find e^2/hc at the end of the trail. Instead, I ended up here:
    http://www.btinternet.com/~ugah174/
     
  12. Apr 9, 2005 #11

    marcus

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    whoa! Warwickshire (which you give as your location) is where Stratford-on-Avon is! Not being a whiz at geography I had not made the connection. So, if I understand you, your home is not far from where Shakespeare lived, when he was not busy in London.

    I believe that Yeats also spent some time in Warwickshire, but that is a relatively unimportant association compared with the Stratford-on-Avon one. The local people would hardly have noticed Yeats, and tourists would not want to be told about him. But he was as good a rhymer in his own way.
     
  13. Apr 9, 2005 #12

    Chronos

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    I wanted to expand a bit on neutron stars and CNS. Smolin is a little vague on what might constitute a deal-busting mass. In the paper he states
    "Sufficiently high is certainly 2.5M, although if one is completely confident of Bethe and Brown’s upper limit of 1.5 solar masses, any value higher than this would be troubling."

    More to the point, I am intrigued by the notion that physical constants are free to choose arbitrary values when emerging from whatever it is they emerge from. Could it be there is only one truly abitrary constant and the others are forced to fall in line once the 'master' constant has chosen a value? Or could it be the universe developes chaotically, where the fundamental constants are initially arbitrary but self tuning until a stable configuration evolves. What I'm visualizing here is the universe not freezing its adjustable parameters until finding a stable combination that allows it to lose its negentropy by creating atoms, stars, etc.
     
  14. Apr 9, 2005 #13

    Kea

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    Winter approaches

    For some of us, this is more seasonal:

    When all aloud the wind doth blow,
    And coughing drowns the parson's saw,
    And birds sit brooding in the snow,
    And Marian's nose looks red and raw,
    When roasted crabs hiss in the bowl,
    Then nightly sings the staring owl,
    Tu-who;
    Tu-whit, tu-who: a merry note,
    While greasy Joan doth keel the pot.

    William Shakespeare, Love's Labor's Lost
     
    Last edited: Apr 9, 2005
  15. Apr 9, 2005 #14

    marcus

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    that's right! Keas and Kiwis get winter :yuck: at the Other time of year!
    our sympathies.

    I was curious about an apparently unfavorable reaction to the main idea here, which you posted in another thread:

    "These prejudices are so invasive that they pervade even the best work in LQG. Picture a Black-Holes-Generate-Baby-Universes scenario...always described from the viewpoint of a metametaobserver, which the theory says cannot possibly exist!"

    The paper where Smolin discussed this idea did not use any LQG formalism (Smolin does write papers which are not LQG research! :smile: ). "Scientific Alternatives to the AP" was what i would call a philosophy of science paper. It dealt with the logical possibility of a connection between hole and bang in a general way.

    Your post contains the suggestion that there are actual LQG papers qualifying as some of "the best work in LQG" dealing with the hole-to-bang connection. I have not seen any LQG papers that do this, exemplary or otherwise. If you actually know some please give me links to them! I would love to read them.

    As far as I know the bang singularity was only removed in 2001 and replaced by a bounce from a prior contraction (but Bojowald did not identify this contraction as coming from a black hole, he simply extended the model somewhat back in time to before the classical singularity without identifying what was there).

    And even if Bojowald HAD mentioned that the prior contraction phase that he discovered looked technically similar to a black hole collapse, I dont suppose that would have made him a "metameta" (not sure what you mean by that), nor would I find it inconsistent with the LQG research framework. If two regimes are found to be mathematically similar one is permitted to point this out.

    All the same, he did NOT speculate as to the nature of the prior contraction phase, and one reason is that, far as I know, the hole singularity has technically still not been removed! One still has to find out WHAT THE BLACK HOLE COLLAPSE LOOKS LIKE MATHEMATICALLY, before one can compare that with the contraction prior to the classical singularity in cosmology. Some preliminary results by Ashtekar and Bojowald have appeared, but nothing like a hole to bang "scenario" is discussed there.

    In seeming contradiction, your post suggests that there are several exemplary LQG papers which "always" describe the hole to bang "scenario" is a certain fashion. I regret to say that this is disconnected from the reality of the LQG literature that I know. And I have been watching the LQG literature rather closely for a couple of years. So what you hint at in your post surprises me and excites my curiosity.

    I will fetch you a non-LQG paper (Husain, Winkler) exploring the hole singularity and finding a bounce. As I recall, Husain and Winkler use the ADM variables, as in the Wheeler-deWitt formalism, no spin networks, no Ashtekar variables. They use their own extension of pre-1986 pre-LQG quantum gravity. Husain and Winkler's methods are also used by Modesto, who derives a bounce in the hole by means he says were "suggested" by LQG---this is related to LQG but not very representative. A second Ashtekar and Bojowald paper (which would be more representative) is said to be in preparation and I hope to see it before very long.

    And I shall hope that in return you will provide me with some links to already posted LQG papers which treat some case of a black hole and derive a bounce (even if they dont explicitly say that the bounce is part of a "scenario").

    This would be essential before we can sensibly talk about LQG papers "always describing" a hole-to-bang "scenario" from whatever viewpoint.
    :smile:

    And by the way, i am rather confident that in the future LQG WILL finish removing the hole singularity, and will find a mathematical resemblance between the prior-to-bang contraction and the contraction down the hole. I see clear signs that LQG will study this possible connection, to see if it works at a technical level.

    I have no way of telling whether technical compatibility will be found when they examine the hole and bang ex-singularities. If a theoretical JOINT is made then the prior contraction is PART OF OUR UNIVERSE and we can look for various observable signatures that might serve to check the theory.
    If LQG does not find compatibility then all bets are off although I suppose some other quantum gravity theory might.
     
    Last edited: Apr 10, 2005
  16. Apr 10, 2005 #15

    marcus

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    Lets get the links for the Husain Winkler and Modesto papers about black hole bounce. Even tho Husain and Winkler are not using representative LQG methods they are still interesting.


    http://arxiv.org/gr-qc/0410125
    Quantum resolution of black hole singularities
    Viqar Husain, Oliver Winkler
    4 pages

    "We study the classical and quantum theory of spherically symmetric spacetimes with scalar field coupling in general relativity. We utilise the canonical formalism of geometrodynamics adapted to the Painleve-Gullstrand coordinates, and present a non-Schrödinger quantisation of the resulting field theory. We give an explicit construction of operators that capture curvature properties of the spacetime and use these to show that the black hole curvature singularity is avoided in the quantum theory."

    As I say, they use ADM variables (the metric on the 3-manifold, not the connection) which is associated with "Geometrodynamics", the circa 1970 Wheeler deWitt approach, and not typical of LQG.

    My impression was that Leonardo Modesto was not doing regular LQG either, although the TITLE of his second paper says LQG. His first paper's abstract says that his approach is "suggested" by LQG but actually follows
    Husain and Winkler ADM variables formulation. (no Ashtekar variables, no spin networks!)

    http://arxiv.org/abs/gr-qc/0407097
    Disappearance of Black Hole Singularity in Quantum Gravity
    Leonardo Modesto
    9 pages
    Phys.Rev. D70 (2004) 124009

    "We apply techniques recently introduced in quantum cosmology to the Schwarzschild metric inside the horizon and near the black hole singularity at r = 0. In particular, we use the quantization introduced by Husain and Winkler, which is suggested by Loop Quantum Gravity and is based on an alternative to the Schrodinger representation introduced by Halvorson. Using this quantization procedure, we show that the black hole singularity disappears and spacetime can be dynamically extended beyond the classical singularity."


    http://arxiv.org/gr-qc/0411032
    The Kantowski-Sachs Space-Time in Loop Quantum Gravity
    Leonardo Modesto

    "We extend the ideas introduced in the previous work to a more general space-time. In particular we consider the Kantowski-Sachs space time with space section with topology R x S^2. In this way we want to study a general space time that we think to be the space time inside the horizon of a black hole. In this case the phase space is four dimensional and we simply apply the quantization procedure suggested by Loop Quantum Gravity and based on an alternative to the Schroedinger representation introduced by H. Halvorson. Through this quantization procedure we show that the inverse of the volume density is upper bounded and so space time is singularity free. Also in this case we can extend dynamically space time beyond the classical singularity."

    though the title says LQG, the Halvorson approach (that Husain and Winkler say they are using) is not based on Ashtekar-type connection-variables and does not use spin networks. So this may be a cousin of LQG but it is somewhat on the margin: not typical or representative work.

    yes, I checked this paper as well. it quantizes the metric, or rather two parameters that parametrize the black hole metric. that is not what I understand LQG to be about, although some part of it may have been suggested by LQG as the author says. The approach developed by Husain Winkler, and in these papers by Modesto, may be of interest on its own, however!
     
    Last edited: Apr 10, 2005
  17. Apr 10, 2005 #16

    Kea

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    Hi Marcus

    Sorry! In the context (other thread) in which I made that remark I used the term LQG very loosely to refer to anything in mainstream QG outside of Strings and the Third Road and its relatives, including naive spin foam models. This includes the more philosophical papers of Smolin, even if, as you say, they are not technically within the LQG framework.

    We need to sort out some terminology once and for all. Did you do that on PF somewhere?

    As for references to LQG work on BH-BB: as far as I know they don't exist, as you say. By metemeta I was referring to the objective observer of the multiverse. This is a philosophical issue rather than a mathematical one, at this point, although I have not been discussing Category Theory for some time without some physical motivation.

    Cheers
    Kea
    :tongue2:
     
  18. Apr 10, 2005 #17

    selfAdjoint

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    Marcus, the connection of these papers to echt LQG is closer than appears from the summaries. From the Husain & Wincler Singularity Reduction paper:

    Thus at every stage they are comparing their results to Bojowald's, and they are motivated by his success. Notice the reference to "holonomy-like variables". This is along the lines of doing the same thing with a different technique, which has a long and honorable history in science. It could be that their non-Schrodinger representation will become a valued tool in LQG research.
     
  19. Apr 10, 2005 #18

    marcus

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    Hi Kea, I think that is right, (there is no LQG work on the "hole-to-bang" connection) and it is a very interesting point. I am wondering why there is not any such work! It is a striking absence. Maybe I can learn something from it.

    In light of that I was wondering what it is that is so pervasive throughout LQG that it "pervades even the best work in LQG." Because your post indicates that it has something to do with "Black-Holes-Generate-Baby-Universes scenario...always described from the viewpoint of a metametaobserver"

    However I do not know of any LQG work that deals with a multiverse! Please point to some papers which would be exemplary or representative enough to count among "the best LQG work" which has an observer of a multiverse, or any multiverse at all!

    This is very interesting, since I dont consider that Bojowald is describing a multiverse when he removes the BB singularity and extends time back to a prior contraction.

    In my view IT IS JUST THE SAME UNIVERSE so I do not perceive anything different from the normal business of extrapolating back in time except that it does not stop at the former, or classical, singularity.

    So I dont see any new philosophical problem arising.

    If you do please explain it, Kea, since I would be delighted to hear about it.

    thx, I have to go help with supper. Back later



    :smile:
     
    Last edited: Apr 10, 2005
  20. Apr 10, 2005 #19

    marcus

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    this, and your other quote are especially interesting because they suggest to me that you think using Category theory solves some philosophical difficulty from which "even the best" or at least some representative LQG work suffers.

    As far as I have seen, LQG has not lead to what is usually thought of as "multiverses". Although by resolving the BB singularity and pushing back to a prior contraction, it may SEEM to some people that Bojowald has crossed some "philosophical" boundary. To me, he has simply extended the universe back a few moments in time beyond where we used to go!

    However, I compare this to what you say here, Kea

    again I regret to say I have to go out shortly. But this is quite a stimulating bunch of ideas and i am looking forward to getting back to you and selfAdjoint!

    cheers, :smile:
     
  21. Apr 10, 2005 #20
    if each black hole leads to new universe then doesn't that imply a different one thus your "multi"tude of uni"verses" or is it the same one everytime and if you rewind the bigbang back to it's supposed e-verse universe where everything is mirrored and time runs backwards then does that imply a possible infinite universe somewhere else contracting to a crunch and then bang another one forms or is it the same one

    so basically is it one universe at a time with a parrallel negaverse runing backwards or many universes all different running in multiversal time which an observer will never see as we will always be locked into our 4d one where time runs forward

    pardon my ignorance but it was kinda where I was going with the white hole thread
     
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