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Un-Standard Model

  1. Nov 26, 2006 #1
    I read here:
    http://www.physorg.com/news78689736.html
    that so called Standard Model only explains ~ 5% of the mass of the universe. Is this not conclusive evidence that this model is falsified--is it not time to give up the ghost and move on ? The Standard Model derives from mid 1960's, and we only get 5% understanding of something as fundamental to physics as mass present in the universe after all these years of effort. Why do governments continue to fund research on this model ? Not trying to step on feet of those that work in this area of research--but 5% predictability in science is pathetic. Yes, yes, of course the Standard Model does a good job in the 5%--but I find this argument wanting. So let this thread begin a discussion of how we are to reach understanding of the missing 95% of mass in the universe.
     
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  3. Nov 26, 2006 #2

    EL

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    Eh, I would say the standard model has a predicatablilty of something like 99,9% within the area it's supposed to work within.
    Would you aslo suggest stop funding cancer research because there's no hope it will solve AIDS?
     
  4. Nov 26, 2006 #3
    As stated, I find 99.9 % of 5% wanting. And why do you state there is no hope to solve Aids, I see great hope in the science of genetics, let us be thankful that Standard Model of physics is not used to study Aids.
     
  5. Nov 26, 2006 #4
    Just because 95% of the mass of the universe isn't covered by the Standard Model doesn't mean you've only an understanding of 5% of phenomena. At present we've an understanding of more than 90% of all observed phenomena (closer to 99%). Dark matter/energy do very very little, if they did more, we'd have spotted them years ago!

    There are plenty of extensions to the standard model in the works. Things like supersymmetry being a big one and might be a big contender for explaining what dark matter really is.

    So while we can't explain what most of the mass of the universe is, we can explain what most of the processes in the universe (that we know of).
     
  6. Nov 26, 2006 #5

    marcus

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    I don't think we can suppose that the so-called "dark energy" effect (a measured acceleration of expansion) is due, in fact, to an actual energy.

    In mainstream cosmology it is treated as a cosmological constant Lambda, which is a CURVATURE, not an energy, and not a mass.

    A recent NASA news conference reported on a new study with z>2 supernovae which simply confirmed that the acceleration matches what one would expect with a constant curvature Lambda-----the data continues to fit a cosmological constant.

    Calling Lambda an "energy"----namely "dark energy"-----is something you get in popular science reporting, but it is misleading. The public gets the wrong idea.

    I think a professional cosmologist (unless talking to a pop sci journalist) would NOT tell you that Lambda arises from some undiscovered particle, or matter field.

    It MIGHT, but then again it might not----the cosmological constant could be a feature of our understanding of gravity---a term in the Einstein equation---with some different basis. Einstein put it in his equation circa 1920 and he did not think to say that it might correspond to a particle!
    :-)

    So that "dark energy" people refer to as 70 percent of the "total mass" of the universe may just be an intrinsic curvature.

    Rigorously speaking you cannot say that the Standard Model only covers 5 percent of the mass because 70 percent of what you are treating as the total may not correspond to any kind of matter that a model of matter like the SM should be describing.

    People DO talk that way because it sounds exciting and makes a good sound bite.

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

    Every physical theory has a DOMAIN OF APPLICABILITY----a range of stuff it is supposed to make predictions about and give useful descriptions of. I think we do not yet know that "dark energy" refers to anything you would expect the SM to explain or predict.

    I think you are possibly right about "dark matter" which is commonly estimated at some 25 percent of the imagined total, or some 5 or so times the amount of baryonic matter.

    People who work on extensions of the SM, in fact DO come up with possible candidates for "dark matter".

    Dark matter appears to clump or coagulate under the influence of gravity. So it behaves somewhat like a fog of particles might be supposed to behave. A concentration of mass associate with a cluster of galaxies appears able to pull in dark matter, so a halo of dark matter can form around visible matter.

    That is particle-like. Maybe some extension of the SM will successfully predict a DM particle. But dark energy does NOT gather together under the influence of gravity. All measurments indicate it is perfectly spread out. Constant throughout space and time. That suggests not some free-floating form of matter, but, if anything, a property of space itself.

    so I think SM can be excused. Dark energy is more in the Quantum Gravity department. (And in fact Smolin has a 2002 paper called "Quantum Gravity with a Positive Cosmological Constant"---work on QG with postive Lambda is ongoing.)

    the point would be, I think, not to stop trying to improve the SM, but to also move ahead with QG towards a more fundamental understanding of space and time.
     
  7. Nov 27, 2006 #6

    EL

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    I was not! I was stating that cancer research will not solve AIDS. In the same way the Standard Model is very unlikely to solve the dark matter problem. But for similar reasons that we go on researching about cancer although it will not say much about AIDS, we go on studying the Standard Model although it probably won't say much about dark matter.
    Cancer research do great within its area of applicability (i.e. cancer), and so is the case for the Standard Model too.
     
  8. Nov 27, 2006 #7

    ahrkron

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    Not at all. The concept of falsifiability refers to predictions of the model within its domain of applicability. As others have stated in this thread, the SM does not cover effects that are mainly gravitational in nature, as the dark energy seems to be.

    The mid 60's, plus pretty much all experimental outcomes in particle physics since then! Just as recently as this year, CDF made public its result on the mixing between the Bs meson and its antiparticle, and it is right on the value predicted by the SM.
     
  9. Nov 27, 2006 #8
    Hi Marcus,

    Read section 1.1 -- "The many faces of the cosmological constant" in the paper by Padmanabhan ("Cosmological Constant - the Weight of the Vacuum") [hep-th/0212290], specially eq. (3) and discussion that follows.

    Best regards,
    Christine
     
  10. Nov 27, 2006 #9

    marcus

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    thanks Christine! I will look at it. I should have said something like this: one CAN interpret the cosmological constant as telling us about a vacuum energy----roughly analogous to a vacuum energy arising in Quantum Field Theory, but a different magnitude.

    I will see what Padmanabhan says. My take on it is that this is very far from a foregone conclusion. One may suppose that Lambda arises from some vacuum energy intrinsic to space and constant throughout all space and time----but there are a number of OTHER speculations as to how it might arise.

    Some ways that it could arise have nothing to do with the Standard Model of particle theory, or with matter. So the point I want to make (perhaps too emphatically) is "don't blame the Standard Model" if it doesn't give you a particle-or-field-or-vacuum-energy that explains Lambda!

    It is not necessarily the SM's "responsibility" to do that, after all it is only particle physics----it is not a quantum theory of space, or of the connection of geometry with matter.

    I will look at Padmanabhan's article, as you suggest, maybe he will give me a different perspective, and I'll get back to you.

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

    Yeah, as he says, eqn. (3) treats Lambda as an "adjustment of the zero point energy". That is certainly one way to look at it! I would take issue with Padmanabhan if he said that one must look at the cosmological constant that way, but I don't see him saying that anywhere. Am I missing something?
     
    Last edited: Nov 27, 2006
  11. Nov 27, 2006 #10
    Hi Marcus,

    What I meant was simply that there are several possible interpretations for Lambda, as one can see for instance in the nice review by Padmanabhan (I might print out a poster of eq3 and hang it on my wall :biggrin: ); that is, the curvature interpretation is not the only possible one (nor it is clearly favoured over some other at this time). I guess in the end we have an agreement that the problem of how to interpret Lambda from the observations and theory is quite far from clear. This was something I was trying to point out in my previous post by calling the attention to Padmanabhan's exposition.

    Thanks,
    Christine
     
    Last edited: Nov 27, 2006
  12. Nov 27, 2006 #11
    Sorry, I did not understand your argument at first. There is evidence of link between HIV (Aids) and different cancers(from:http://www.cancerbackup.org.uk/Heal...s/BMEQAs/CurrentQAs/related_faqs/QAs/76780112)

    "As AIDS progresses, the immune system becomes weaker. As it becomes weaker the risk of developing certain cancers increases. These include Kaposi's sarcoma, certain types of non-Hodgkin lymphoma, and cancer of the cervix (the neck of the womb). These cancers are known as 'AIDS-defining cancers'. This does not mean that everyone who gets one of these cancers is HIV positive, or has AIDS. Most lymphomas and cervical cancers occur in people who have never been HIV positive and who do not have AIDS. There is also evidence that some other types of cancer occur more often in people with HIV infection than the rest of the population. These include anal cancer, Hodgkin lymphoma, angiosarcoma and multiple myeloma."

    Anyway, I do not think that, once a verified model for dark matter is found, that this new model will explain 95% of mass in universe, but good old current Standard Model will continue to explain rest of 5%. I suggest the new future explanation of 100% of the mass in the universe will completely do away with the current Standard Model. My point for this thread is to discuss what this new model may be--the mathematics and dynamics of it.
     
  13. Nov 27, 2006 #12
    Dark matter/energy may be in quantum superposition with the 5% we observe--they may "do" much to form the reality. And did not Bohr model of atom work just fine in its time, allowing for 99% understanding of atom in 1913, only to be replaced--why not same fate for SM--that it will become an obsolete scientific theory (http://www.cancerbackup.org.uk/Heal.../BMEQAs/CurrentQAs/related_faqs/QAs/76780112), just as Bohr model ?
     
  14. Nov 27, 2006 #13
    I have a question, in the paper (which can be viewed here:http://arxiv.org/PS_cache/hep-th/pdf/0212/0212290.pdf) there is this comment:

    "As long as (ρ + 3P) > 0, gravity remains attractive while (ρ + 3P) < 0 can lead to repulsive gravitational effects. Since the cosmological constant has (ρ +3P) = −2ρ, a positive cosmological constant (with  > 0) can lead to repulsive gravity."

    My question is, can this "repulsive gravity" also be considered to be the term "anti-gravity" -- that is, does this paper provide mathematical argument for potential existence of anti-gravity in universe ?
     
  15. Nov 27, 2006 #14

    marcus

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    there are several competing quantum theories of gravity being constructed which are explicitly background independent.

    discussion of 3 or 4 different approaches is gathered in a book to be published next year by Cambridge U. Press called

    Approaches to Quantum Gravity: Towards a New Understanding of Space Time and Matter

    the editor is Dan Oriti and there are about 20 or so authors included in the book. there is also Q and A discussion between the authors of different approaches

    some string theory writings are included even though string is not primarily a background independent approach---it may achieve an explicitly B.I. formulation in the future.

    At this point the best one can do is give a balanced discussion of several approaches to a quantum theory of space, time, and matter. That is what is called "Quantum Gravity". Increasingly modern B.I. Quantum Gravity deals with particles, matter, as well as geometry of spacetime. In several recent papers MATTER arises from the same stuff or degrees of freedom as geometry----different particles and their interactions emerge as aspects of geometry, in a way.

    the picture is confusing. Hopefully Oriti's book will clarify the picture somewhat. Several of the approaches being worked on seem to be converging----they have points of similarity. but it is still a chaotic diverse field of research.

    maybe i can get some links that will suggest the range of QG options.
    ================
    Just a side comment, You mentioned repulsive gravity. Repulsive gravity at very high matter-densities is one of the things that comes out of Loop Quantum Gravity models of both the collapse of a star to form a black hole and also the big bang (which LQG models suggest was a bounce)------so repulsive gravity is something one sees emerging from the analysis as a quantum effect-----but that is not what Padmanabhan was talking about he was describing the acceleration of expansion driven at very LOW near-vacuum densities by the cosmological constant. the cosmo. const. is a term in a classical (non-quantum) equation. QG may eventually be able to explain it as a quantum gravity effect but that is a very nebulous notion. In our era, despite the cosmo const., gravity is predominantly attractive----the LQG analysis, where it turns repulsive at high density, was unexpected and AFAIK unconnected with the presentday accelerated expansion of nearly-empty space
    ================

    So far I think the QG researcher who has been most notable for getting matter, and indeed the Feynman diagrams that show how matter interacts in conventional QFT, to emerge from a quantum theory of spacetime geometry is a guy in Canada named Laurent Freidel.
    In his work it is clear that he is building a quantum theory of space, time, AND matter.

    You can probably google the name Freidel, or including his first name Laurent, and get a bunch of articles and references.

    his uses so-called SPIN-FOAM approach, and also "group field theory"-----he gets particles as a kind of aspect of geometry (like a tangle or a fault-line in spacetime) and he gets Feynman diagrams as the flat limit (as gravity is turned off) of his spinfoams.

    Freidel is not the only one working in that direction but I always seem to be waiting for his next paper, hoping it will clarify some unresolved question.

    So far there have been no final triumphs or complete successes
    ====================

    eventually I suppose there will have to be a B.I. quantum theory====where the continuum is floppy (no fixed geometry)=====and where particles or fields arise from the same stuff as geometry, so that matter is an aspect of geometry=====and where MATTER AND GEOMETRY INTERACT in a natural way, as they do in Einstein's 1915 equation of GR, but in that classical theory the interaction whereby matter curves space is only described by an equation, and not explained

    and this quantum theory must be applicable to regimes of very high curvature, very high density and pressure, like the big bounce, or the collapse of a star to form a black hole---in other words to extremely dynamic situations with violently changing geometry =====this is one reason that many people think the ultimately successful theory will have to avoid preconceived background geometry, which is just not realistic in these extreme situations, and will have to be B.I.
     
    Last edited: Nov 27, 2006
  16. Nov 28, 2006 #15
    Its not even evidence that the model is wrong, let alone conclusive. Is the mathematics of real numbers wrong because it doesn't include complex numbers, vector or matrices? It is just incomplete. Rather than throw it out because it is wrong it is more sensible to complete it, because it is correct where it can give an answer. Like every model it is incorrect where it can't give an answer... this is not suprising, it is expected.

    If the model was not correct where it is intended to be correct, then you throw it out, and only if it is wrong enough to be useless...

    We need to have lots of knowledge of how far the Standard Model applies. Any good model must tend towards the Standard Model in its domain of applicability. Also, when we find the places where it breaks down in the laboratory we can start making experiements that can test other models. At the moment what research can we do into other models? We don't have dark matter stored in laboratories, and we can't collide supersymmetric particles in our accelerators yet... its just a case of incremental steps. What other research would they spend their money on? We can't test predictions of better models until we have better equipment and materials, which most likely means that we need to go beyond the SM energy scale, which means we need to research the SM scale first... etc...
     
  17. Dec 6, 2006 #16
    Epicircles were not thrown out because they were useless. They were very usefull - and correct - at predicting planetary motion. Regardless, the Epicircle model was wrong.

    Well, I'd say we continue research on the SM scale because that is the currently "winning" model. We can tweak it and "verify" it with experimentation but "proving" it as a valid description of the physical world will be very difficult. In the mean time it concerns me that so many in the field seem to blur the destinction between a working model and reality.

    Reality may one day prove to be quite different than what has been described in SM, but the adoption of reality will not come without revolution.

    I searched but can't find the exact quote.. *sigh*.. but I recently saw a SciNet piece on the Cosmological SM in which Dr. Disney said something to tune of "Current knowledge is a barrier to advancing knowledge."
     
  18. Dec 6, 2006 #17


    Wrong on every count.

    I don`t think anyone here understands this sad fact better than you.
     
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