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Asymptotic freedom,quantum gravity

  1. Sep 16, 2004 #1
    The idea of a singularity is a problem for Big Bang cosmology and
    the singularity general relativity says existed at the start of the universe needs to be removed.There are singularities predicted for black holes too.
    Isn't the most likely explanation, to stop a singularity from forming, that
    gravity gets weaker for some reason when mass gets beyond a certain density? Since current theory cannot explain such a scenario,
    we would expect the correct theory of quantum gravity to show that
    gravity does in fact get weaker above a certain mass density,
    and that the underlying reason is a gravitational coupling constant
    that has become weaker? Could gravity show asymptotic freedom of some kind for masses separated by short distances? What are your thoughts on this?
  2. jcsd
  3. Sep 16, 2004 #2
    asymptotic freedom is inherent to the strong force not gravity...so you should be looking to the quarks in this case...

  4. Sep 16, 2004 #3
    I am afraid singularities could be real object occuring in Nature. You are right, only quantum phenomena could erase those. We don't know really, and this is speculative. It has often been argued that one only needs the "blurring" of QM. The world would be simpler if singularities were artefacts.
  5. Sep 16, 2004 #4
    asymptotic freedom is inherent to the strong force not gravity...so you should be looking to the quarks in this case...

    Rothie M:

    Is there a qm rule that says a spin 2 boson can't have a colour charge?
    Perhaps gravity just stays constant at short distances.
    Last edited: Sep 16, 2004
  6. Sep 16, 2004 #5
    A rule ?? No, it is even more easy to answer that : THE DEFINITION.

    Gravitons mediate the gravitational-interaction, not the strong force.

    Could you even imagine what would happen if gluons (they carry colour) would be directly connected to gravity???

    No, ofcourse this is speculative and even a sumb question because gluons DO NOT HAVE THAT PROPERTY... :smile:

  7. Sep 16, 2004 #6
    Could you even imagine what would happen if gluons (they carry colour) would be directly connected to gravity???

    Rothie M:
    The force carrier for gravity has to be spin 2 but it does not have to be a graviton.
    Some GUTs say that even electrons are made from quarks - but the colour force on these quarks must be weak or else we would see electrons involved in strong interactions.Perhaps gravitational force carrier could carry a weak form of colour charge.Of course there is no way of knowing this at the moment.
  8. Sep 16, 2004 #7
    Rothie : you really have a very powerful imagination. This is obvious in the numerous ideas you have been throwing lately. But you desperately lack rigor. One guy I am working with can throw like ten ideas every 15 minutes. So few are useful. The useful ones : nobody else could have. That is what makes him so precious.

    I really doubt you have studied QFT properly. The current model is based on symmetries. Those force carriers come from symmetries in different space. GUTs relate such spaces, but they are speculative.

    By the very definition (once again) the graviton is associated to gravity !

    You could pretend the graviton carry color, but this is immediately plagued by confinement.
  9. Sep 16, 2004 #8
    Hey Marlon : we are science advisors !!! :approve: :tongue2:
    I am so proud. I could never dream they would award us !
  10. Sep 16, 2004 #9
    By the very definition (once again) the graviton is associated to gravity !

    Rothie M;

    Yes but spin 2 is the force carrier whether or not the graviton is that carrier.For my idea to be right colour would have to come in smaller units just like electric charge on protons is + 2/3 +2/3 - 1 / 3.
    You are right - I haven't studied qft in great mathematical detail but I have had alot of information given to me here and on the research forum.But I work on the basis that
    no matter how complex the maths that describes a particle system, that system is still
    made from particles (I am well versed in wave/particle duality too!) and particles
    only have a few simple properties associated with them.The maths of physics can be hard to understand but good physical principles which come from the maths never are.I take an interest in physics because its results are interesting and can be put to practical use.Most of the qft I know comes from Wikipedia, this forum and some of Feynman's writings.
    Last edited: Sep 16, 2004
  11. Sep 16, 2004 #10
    Sometimes imagination does not need rigor. Sometimes it even needs to be free from the constrained formalism !

    The problem is that color is a very specific property. It has been named exactly because of that : confinement. It is unlikely to me that you can have one third of red. Mesons and baryons, (1-1=0) or (1+1+1=0) that is all. I might have a too simple and flawed conceptions. For instance, I do not believe the pentaquark was a real signal.
  12. Sep 16, 2004 #11
    :smile: Rothiemurchus

    Red in smaller units ??? remember that the colour itself is the quantum-number and it has no assigned number to it.

    Besides quantumnumbers arise from symmetries and conserved physical quantities. The Noether-Theorem (Emmy Noether to be exact and yes she was a woman) states that with every symmetry in physics there is a conserved quantity. When making this global symmetry local (local means dependent on time and space, and this is necessary for the sake of covariance and locality in field-theories like a charged particle interacting with an EM-field) extra fields arise in the theory. These fields describe the gauge-bosons or the force carriers.

    Now, the interaction between fermionic matter-fields happens through exchange of the force-carries. The interactions are determined by a "judge", ie the conserved quantity. For example charge-conservation states that the net effect of some interaction must be that the charge must remain the same as before the interaction. Just the same with the colour-quantumnumber. Mathematically all this can be constructed, checked and verified by grouptheory and the possible spin-values of some particle arise from this approach.

    So basically you cannot assign a spin to some particle or make statements about the colour-quantumnumber without following the above procedure...

  13. Sep 16, 2004 #12
    Thanks for your remarks Humanino and Marlon.It is good that you are
    willing to help an amateur like me.I do listen to what more knowledgeable people
    say even if it does not always seem so!
    And I was surprised when I first read that Noether was a woman.
    Considering how important her theorem is you would think
    that feminists would emphasise her contribution to science a lot more -
    she is not well known even among physicists perhaps.

    I do not believe the pentaquark was a real signal.

    Rothie M:

    Wilczek and Jaffe at MIT model pentaquarks as two diquarks
    (an up-down pair) plus an anti-strange.The diquarks have colour and spins in
    different orientations which apparently amounts to low energy.They are trying to build the equivalent of Mendeleev's periodic table using the diquark idea.But at the moment no-one knows for sure that 4,5 and more quark particles exist.
    Last edited: Sep 16, 2004
  14. Sep 16, 2004 #13
    I will always emphasise on the contributions of women in science and all other possible fields of expertise...BRAVO per tutte le belle donne nel mondo :cool: :cool: :cool:

    Rothie, feel free to ask more clarification if you wish.

    May I ask : how old are you and what do you study, just curious...

  15. Sep 16, 2004 #14
    I am 39 years old.I graduated in chemistry in 1988 (Aberdeen university Scotland).But I do not use my chemistry degree nowadays.I have always been interested in physics but couldn't stand the way it was taught at school.QM was a large part of my chemistry degree.
  16. Sep 16, 2004 #15
    Ahh, you are from the country of Sean Connery...nice one
  17. Sep 16, 2004 #16
    Yes, theoreticians first got all excited by this new discovery. Even more, some of them have been suggesting for decades experimentalists should look for them. Yet, people are changing their mind recently. None of the high-energy facilities has seen any, only mid-energy ones. Besides, dedicated experiments tend to delay publications of the results. It might very well be that the poor-statistics evidences were wrong. It also very doubtful, that the width is so small, and the mass do not agree within a much larger error bar. AFAIK theoreticians are puzzled by such a small width.

    If I had to bet today, I would bet that was a mistake. We only have to wait for a few weeks now to have the definite answer. Let us be patient.
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