Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Alternatives to GUT and GUT Epoch

  1. Dec 3, 2013 #1


    User Avatar

    I went to a science museum last weekend and saw timeline of the big bang. There is a "GUT Epoch" mentioned at the beginning but then how can this be when GUT (Grand Unified Theories) was not proven due to lack of proton decay, etc. What other alternatives beyond the standard model if the strong force and electroweak was not really combined force early in the universe? Do you think this is more possible than symmetry unifying them? Would Big Bang no longer be so if they indeed came off separately? What is the list of ideas or scenerios about this in arxiv, etc.? What candidates of the mechanism?

    Without gauge symmetry unifying the strong and electroweak force. How do you think (or possible scenerios) how they separately came to be? I'm sure Loop Quantum Gravity people prefer this as their theory doesn't unify the forces but just cooking up quantum version of gravity.
  2. jcsd
  3. Dec 5, 2013 #2


    User Avatar

    Something's not right. Proton in GUT is supposed to decay in 10^72 years.. more than the lifetime of the universe... so what scientists do is to put 10^72 protons in experiments and see if one would decay. Since it didn't, then GUT as least SU(5) is falsified. Does the logic hold? It's like saying that there is a 1/10^72 chance a prisoner can quantum tunnel outside a prison cell and by creating 10^72 prisoners, one of them can indeed tunnel... does this makes sense?

    If it didn't, then Proton can decay in 10^72 years, isn't it and GUT at least SU(5) is still promising.
  4. Dec 5, 2013 #3


    User Avatar
    Science Advisor

    The current experimental constraints on the minimum proton half-life are between 10^33 and 10^34 years. This rules out SU(5) at (at least) 90% confidence. Other GUTs predict longer half-lives.
  5. Dec 10, 2013 #4
    Only SU(5) GUT - which is the simplest but not the favorite GUT - has been ruled out by proton decay experiments.
  6. Dec 10, 2013 #5
    First, the Number is 10^30ish. Not 10^72. 2nd, Yes, by increasing the sample size even very unlikely events ought to be observed.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook