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Elementary/fundamental particles

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    Why are fermions and bosons still referred to as fundamental particles, rather than strings (or branes, since strings are merely 1-branes)?

    And before people simply say that it's called string THEORY for a reason, I'd rebut that quarks too have not been directly observed (although we do at least understand that it's due to the colour force), so I'd argue there is almost as much evidence for strings and branes as there is for other compound subatomic particles (particularly following the observed negative correlation between discrepancy between theoretical and experimental results and accuracy of mathematical constants a few weeks ago in proton-proton collisions at CERN's LHC).
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    Well, this has turned into a lively debate... :rolleyes:
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    String theory is an attempt to marry QM with GR. As far as research in QM is concerned, it may as well carry on as it has until this 'better' framework has been more fully developed - by which I mean, substantial empirical evidence. I recall ST having some major experimental failures, whereas QM has been basically bulletproof.
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    (Original post by i.am.lost)
    Well, this has turned into a lively debate... :rolleyes:
    There isn't many people that understand postgraduate physics on TSR lol
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    (Original post by i.am.lost)
    quarks too have not been directly observed .
    http://en.wikipedia.org/wiki/Deep_inelastic_scattering
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    From that link, "due to quark confinement the quarks are not actually observed but instead produce the observable particles by hadronization".

    It is not possible to isolate or directly observe quarks. Obviously I'm not denying their existence, all mathematical models and experimental evidence point to their existence and we've been able to map out their characteristics and behaviours fairly well. But my point is, there isn't a huge distinction between the evidence available for quarks and for strings.
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    (Original post by FireGarden)
    String theory is an attempt to marry QM with GR. As far as research in QM is concerned, it may as well carry on as it has until this 'better' framework has been more fully developed - by which I mean, substantial empirical evidence. I recall ST having some major experimental failures, whereas QM has been basically bulletproof.
    M*-theory's equations don't predict anything that has been experimentally proven wrong, it agrees with observable properties, and it's the only major theory which actually accounts for the existence of gravity.

    The only weakness is its inability to generate exact answers, since the equations are too complicated for today's technology, so the equations and results are approximations relying on perturbation theory.

    But you can't fault the theory just because we lack the framework to support it. It would be like calling a calculator without batteries broken...
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    (Original post by i.am.lost)
    M*-theory's equations don't predict anything that has been experimentally proven wrong, it agrees with observable properties, and it's the only major theory which actually accounts for the existence of gravity.
    because it's been fine-tuned to agree with current understanding

    The only weakness is its inability to generate exact answers, since the equations are too complicated for today's technology, so the equations and results are approximations relying on perturbation theory.
    and a serious inability to be tested in any meaningful way

    Do you actually know anything about string theory beyond a few popular science books? I mean, this is not a postgraduate question in any sense of the word (you're not actually asking a question, you're coming to air your personal grievances as to why your favourite theory isn't considered seriously by the majority of people who actually DO physics).

    Deep inelastic scattering does provide experimental evidence of quarks (it suggests some kind of internal structure inside baryons and mesons which happens to have the same properties QCD predicts), and hence QCD already has a lot more experimental evidence than any string theory. Strong theory has led to a lot of advances and developments in mathematics in the form of new knot invariants and a better understanding of n-categories, but in terms of actual physics we can test, not so much.

    I'd suggest reading 'Not Even Wrong' by Peter Woit as one of the few popular science accounts actually critical of string theory.
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    (Original post by around)
    because it's been fine-tuned to agree with current understanding



    and a serious inability to be tested in any meaningful way

    Do you actually know anything about string theory beyond a few popular science books? I mean, this is not a postgraduate question in any sense of the word (you're not actually asking a question, you're coming to air your personal grievances as to why your favourite theory isn't considered seriously by the majority of people who actually DO physics).

    Deep inelastic scattering does provide experimental evidence of quarks (it suggests some kind of internal structure inside baryons and mesons which happens to have the same properties QCD predicts), and hence QCD already has a lot more experimental evidence than any string theory. Strong theory has led to a lot of advances and developments in mathematics in the form of new knot invariants and a better understanding of n-categories, but in terms of actual physics we can test, not so much.

    I'd suggest reading 'Not Even Wrong' by Peter Woit as one of the few popular science accounts actually critical of string theory.
    I find it interesting how you're criticising me personally rather than the argument I've put forward... While I'm not a physicist, I've been exposed to enough particle physics to be able to come to my own conclusions, and this was intended to be a discussion open for debate, not an actual question. So my background is actually quite irrelevant.

    I don't know what it was about my earlier posts that you seem to misunderstand, but I don't need you to convince me that there's evidence for the existence of quarks. I'm just saying that simply because we don't have the tools to test M-theory predictions (although some early results are beginning to trickle pointing towards its validity), its implilications have not been fully accepted by the field despite being arguably the best unifying model available.

    Thanks for the book tip, I've come across Woit's blog previously and his arguments against string theory are actually wafer-thin. It's difficult for critics to argue against mathematics.
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    (Original post by i.am.lost)
    words
    I'm going to be blunt:

    'I've been exposed to enough particle physics to be able to come to my own conclusions'

    no you haven't.

    'this was intended to be a discussion open for debate, not an actual question'

    in a forum mainly populated by sixth formers looking for homework help?

    ' It's difficult for critics to argue against mathematics.'

    precisely why they're arguing against it. it's maths, not physics. there's a difference.

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Updated: April 18, 2012
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