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Questions about fundamental interactions, uncertainty principle and entanglement.

  1. Sep 7, 2010 #1
    Hello, I have several questions, perhaps not correctly asked, however I must get the concepts right, I'm intrigued. :bugeye:

    1. What does it mean that the strong force is 137 times stronger than EM force?
    2. Are particle collisions in particle physics also considered as wave-collisions with interference, or as classical particles? (I did some basic work about the Z boson's mass, using relativistic particle kinematics where properties of the electron-positron pair emitted were used to deduce the Z's mass)
    3. I have heard that the top-quark does not create hadrons, but decays via the weak force directly, unlike other quarks. Why is that?
    4. Are there any decays via the strong and EM force at all? or only via weak force (quarks to leptons and vice versa)?
    5. I know that a particle's mass (for example Z boson's mass = 91 GeV) is not a *real* mass, but only the value that is most likely for us to measure. The uncertainty principle dictates that every particle mass is "smeared" (to give a Breit-Wigner probability distribution), just like a particles's position is "smeared" and called a wavelength. I also know that because of the uncertainty principle, energy conservation can be broken for a short period of time, enough to let the virtual heavy Z\W bosons form so weak interaction can take place. But if the Z or W can even be 5 GeV, what does it even mean that they are "heavy"? Why do we need particle colliders at all, to form Z's and W's with high energy, if they can be created form ANY energy, at any state (e.g. radioactivity)?
    6. In the uncertainty principle's time-energy form, where the energy [tex]\Delta[/tex]E could be the mass of a particle, the time [tex]\Delta[/tex]t is only used as time-of-decay, or can be used as something else?
    7. There's a beautiful concept I found on a http://quantumweird.wordpress.com/" [Broken], dealing with quantum entanglement "paradoxes", such as "backwards causality" in the delayed choice quantum eraser experiments, where because in the photon's relativistic reference frame, all distances are 0, and the time of travel is 0, the entangled photos are still touching, and reach their destinations at the same time. This way of thinking apparently solves quantum entanglement not-logical problems. He also mentions that for particles moving at less than C, this is also valid because their internal mechanisms of interaction do move at C. Is this view valid at all? I am very confused with entanglement.

    Thanks a lot. :rolleyes:
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Sep 7, 2010 #2


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    Welcome to PhysicsForums, etamorphmagus!

    You are asking a lot of questions - which is good. They are on several different subjects, so don't be surprised if some get skipped...

    As to quantum eraser type experiments and entanglement: there are a variety of interpretations of QM that purport to explain these experiments in physical terms (i.e. over and above the mathematical formalism). I am not too sure the relativistic treatment at the website you referenced really does much of anything in this regard. It is possible to entangle photons that have never existed in each others' light cone, something which the referenced page cannot hope to explain. Further, such entanglement can be made to occur either before or after the photons are detected.
    Last edited by a moderator: May 4, 2017
  4. Sep 7, 2010 #3
    Hi and wellcome,

    I found your last point very interesting. I am really curious to hear the other's comment.

    Best wishes

  5. Sep 8, 2010 #4
    Thanks for responding.

    Can you elaborate about entangling photons after they are created and entangling outside of their light cones?
  6. Sep 9, 2010 #5
    I am sorry for raising the thread, but apart from the review of the last question, which is more interpertational than actual physical principle, I am quite frustrated with the 5th question, and the actual need of a collider, if the weak force interacts anyways. Why is it then important than the particle has any mass at all if it "virtual" and comes to be at any mass anyways (due to uncertainty of mass).

    This shouldn't be a very difficult to answer, I'm probably missing something.
  7. Sep 10, 2010 #6
    The blog you linked to seemed to be b**lsh*t.

    Wrt your 5th question, does it have anything to do with E=mc^2?

    Wrt entanglement, what is it, exactly, that you find confusing about it? Is it the 'concept' of entanglement. Or the math? Or what concepts one might associate with the math, or what?
  8. Sep 10, 2010 #7
    Yeah fine the blog is not the best place to be educated then.

    Well a lot of energy is necessary to create the weak-force carriers. But in reality, they are created regardless of having enough energy or not, because they break E-conservation for a short t.

    But this isn't my question. I want to know why must the explanation be so, and why are they "heavy" anyways. According to the uncertainty of E-t, they can be measured in the LHC as 10 GeV, or 150 GeV, with the peak being 91 GeV (for Z boson), so what does it even mean that they have a rest mass, if it can be anything at all when measured?

    Also, does in theory we say they must be heavy, unlike photos, because we observe the interaction to be on a very small scale, therefore they must decay rapidly, THEREFORE they must have mass?

    Forget it. I just regard the phenomenon as non-locality, one of the quantum concepts we cannot intuitively understand (I tried too, using that blog).
  9. Sep 10, 2010 #8


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    This might do:
    http://arxiv.org/abs/quant-ph/0201134" [Broken]
    One of the modifications delay measurements after Bell state analyzer (BSA) in respect to (to be) entangled photon measurements. Well it would be better if BSA itself would be delayed but at least I myself don't have any doubt that this would not change result.

    You can try to search for "Entanglement Swapping" if you are interested in other similar experiments.
    Last edited by a moderator: May 4, 2017
  10. Sep 11, 2010 #9
    Thank you zonde, I'll go over those experiments.

    About question #5, someone did answer however the answer was for some reason deleted, but I still got it emailed. I won't disclose the responder's nickname, in case he does not wish that.

    The answer is as follows:
    So what it means, is that we don't use some radioactive material to study weak-force bosons, because the amount of events is too low? Not because of (maybe) the increased distance or time the boson travels in the collider before it decays? I'm just guessing, I really want to understand the whole notion of weak-force study.
    You know what, what about the Higgs? Pretty similar, it's supposed to have rest mass of 100+ GeV, but it's acting all the time, giving mass to all particles. So why do we need the collider? Does it blow it apart and isolates it? And the same thing is done for the Z/W bosons?
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