Alternatives to GUT and GUT Epoch

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Discussion Overview

The discussion revolves around the concept of the Grand Unified Theories (GUT) and the GUT Epoch in the context of the early universe. Participants explore alternatives to GUT, the implications of proton decay experiments, and the potential separation of fundamental forces during the universe's formation.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • One participant questions the validity of the GUT Epoch, noting that GUT has not been proven due to the lack of observed proton decay and asks for alternative theories beyond the standard model.
  • Another participant argues that the logic of using a large number of protons in experiments to test for decay is flawed, comparing it to a hypothetical scenario involving quantum tunneling.
  • A third participant provides current experimental constraints on proton half-life, suggesting that these constraints rule out certain GUT models like SU(5) with high confidence.
  • It is noted that only the SU(5) GUT has been ruled out by proton decay experiments, while other GUTs may still be viable.
  • There is a correction regarding the expected proton decay time, with one participant clarifying that the correct figure is around 10^30 years, not 10^72 years.

Areas of Agreement / Disagreement

Participants express disagreement regarding the implications of proton decay experiments on GUT models, with some asserting that SU(5) is falsified while others suggest it may still hold promise. There is no consensus on the validity of the logic used in the decay experiments or the interpretation of the results.

Contextual Notes

The discussion highlights limitations in the understanding of GUTs and the implications of experimental results, particularly regarding the assumptions made about proton decay and the interpretations of statistical probabilities in experimental physics.

kye
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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.
 
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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.
 
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.
 
Only SU(5) GUT - which is the simplest but not the favorite GUT - has been ruled out by proton decay experiments.
 
kye said:
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.

First, the Number is 10^30ish. Not 10^72. 2nd, Yes, by increasing the sample size even very unlikely events ought to be observed.
 

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