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Unconsidered source of CP asymmetry?

  1. Nov 13, 2013 #1
    I constantly see references to the "strong CP problem" which is basically just the fact that the CP asymmetries in the SM are not large enough to account for the observed CP asymmetry in the universe. What I find odd is that nobody ever mentions the HUGE CP asymmetry caused by our current cosmological model! Since CPT is presumed to be a true symmetry of nature (related to Lorentz invariance), T asymmetries and CP asymmetries are equivalent! The Big Bang, the idea that the universe had some initial time t=0 and is moving FORWARD through time (i.e. entropy increases), presents a nearly complete breaking of T symmetry on large scales. Why is this not generally considered as the source of the observed CP asymmetry??
     
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  3. Nov 13, 2013 #2

    mfb

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    This is not what T symmetry means.
    If you could magically reverse the motion of all particles and even of spacetime itself, the universe would collapse (nearly) in the same way as it expanded. The laws of physics are (nearly) invariant with respect to the direction of time, even if the evolution of matter in the universe is not.
     
  4. Nov 13, 2013 #3

    Avodyne

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    This is not the strong CP problem.

    http://en.wikipedia.org/wiki/Strong_CP_problem
     
    Last edited: Nov 13, 2013
  5. Nov 14, 2013 #4
    Yes, that is why its spontaneous symmetry breaking of T symmetry! The laws of physics are (nearly) T invariant, and yet OUR particular solution (the universe) is not. Our universe is expanding not collapsing. You could also say its our boundary conditions that break the symmetry. Our past is a singularity, but our future is a frozen, maximal entropy universe.

    And yes, Avodyne, sorry I got confused about the name. You are right, this is not the STRONG CP problem, just the general CP problem.
     
    Last edited: Nov 14, 2013
  6. Nov 14, 2013 #5
    The OP doesn't understand T symmetry which is not a symmetry of the state of the universe. It is a symmetry of the equations governing the evolution of the state of the universe. That symmetry is NOT broken by the boundary condition imposed at the beginning of the universe - namely the condition of small starting entropy.

    The OP doesn't understand the Strong CP problem either. The problem is not that the Standard model's CP violation isn't big enough. The problem is that it ought to be much bigger but isn't. Why isn't it? That's the question that must be addressed by any proposed solution to the Strong CP problem.
     
  7. Nov 14, 2013 #6
    I'm just going to point you to my previous post... T symmetry is not a symmetry of the state of the universe, as you said, which means T symmetry is spontaneously broken. The boundary conditions are the beginning and end of the universe, which are NOT time symmetric. As for the strong CP problem, I already admitted I used the wrong term...
     
  8. Nov 14, 2013 #7
    You still don't understand it. Even if your solution is not time symmetric, that doesn't mean that T symmetry has been broken (implicitly, explicitly, spontaneously, or otherwise). T symmetry is not intended as a symmetry of a solution and it doesn't care if the solution is symmetric or not. As long as the equations governing the solution are time symmetric, T is not violated.

    (added by edit) In other words: If a theory is time symmetric, the application of the T operator to a valid solution will create another valid solution but that new valid solution is not required to be the same as the original valid solution. It is a time reversed solution. If a theory is NOT time symmetric than applying the T operator to a valid solution will create an invalid solution (that is not a solution).
     
  9. Nov 15, 2013 #8
    I dont think you understand spontaneous symmetry breaking... It is defined as a solution that does not obey a symmetry of the lagrangian, which is exactly the case in our universe
     
  10. Nov 15, 2013 #9

    mfb

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    It is a broken symmetry, but it has nothing to do with spontaneous symmetry breaking as it is used in particle physics.

    You asked a question, you got answers. If you have more questions, feel free to ask them, but stop posting nonsense as facts.
     
  11. Nov 15, 2013 #10
    WOW that's rude... All I did was provide a definition of "spontaneous symmetry breaking". It is when there is a symmetry of your model that is not a symmetry of the solution... Yes, in high energy particle physics the term usually implies a little more (mainly that its a continuous symmetry that then gives you a goldstone boson) but that is how its defined..

    As for your comment that "it is a broken symmetry" I'm not sure whether you are referring to the explicit symmetry breaking from CP violations in the SM or the spontaneous breaking from the initial conditions of the universe, so I'm not sure how to respond. However, the large-scale structure of the universe GROSSLY violates T symmetry even though the underlying physics respects it
     
  12. Nov 15, 2013 #11

    mfb

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    That is just very direct.

    It does not.
    Our universe is not symmetric, but "T symmetry" refers to the symmetry of the physics, not a (non-existent) symmetry of the state of the universe.
     
  13. Nov 16, 2013 #12
    Which is another way of saying its spontaneously broken isn't it?? Our universe COULD be invariant under T transformations, but it almost universally prefers the forward time direction, breaking this symmetry that is present in the physical laws (approximately)
     
  14. Nov 16, 2013 #13

    Vanadium 50

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    Asked and answered. Several times. Repeating this assertion and continuing to go in circles isn't going to help anything.
     
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