GUT viable w/o SUSY? Could GUT be physically wrong?

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In summary, one argument for Supersymmetry (SUSY) is that it allows for the running gauge couplings of the three forces to meet at around 10^15 GEV, whereas without SUSY they do not meet. This is important for the viability of Grand Unified Theories (GUT). However, even without SUSY, the couplings are close enough to suggest some sort of unification phenomenon. Additionally, the existence of SUSY can improve the unification of couplings in various models, suggesting its attractiveness as a solution.
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ensabah6
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One argument in favor of SUSY is that without SUSY, the running gauge coupling unification do not meet for the three forces, but with SUSY they meet around 10^15 GEV. This implies that gauge coupling most meet for GUT to be viable. So without SUSY, the running gauge couplings do not meet.

If SUSY does not exist, then the SM gauging couplings do not meet. Does this imply that GUT are physically wrong?
 
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ensabah6 said:
If SUSY does not exist, then the SM gauging couplings do not meet. Does this imply that GUT are physically wrong?
Afaik w/o SUSY the gauge couplings are calculated in some order in perturbation theory and are extrapolated over a huge energy range. So for me there is no reason why higher order corrections should not tune the running of couplings.

And as far as I understood GUT is not rules out b/c the couplings do not meet but because all GUTs cause the proton decay too fast.
 
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A lot of this game is very sensitive to new physics and calculational sophistication between the electroweak scale and the GUT scale. Absent knowing that, its very hard to say much of anything exactly.

Keep in mind the couplings almost meet with just the standard model physics, so close that even if SuSY didn't exist, it wouldn't be a bad guess to assume that some sort of unification phenomenology takes over.

So of course, you have the famous selling point for the MSSM where the couplings unite almost perfectly. However I would say its oversold putting it that way, as its a little bit fishy b/c it really assumes very little new physics until the unification scale and could be purely coincidental that it seems perfect to us at this time given our limited knowledge of btSM physics. Instead I would say that SuSY has the attractive benefit that it tends to ameliorate coupling constant unification in a range of generic model(s) building. Thats still nontrivial, b/c a priori you might have expected the fit to simply get worse. That it doesn't is a good sign.
 

1. What is GUT and how does it relate to SUSY?

GUT (Grand Unified Theory) is a theoretical framework that aims to unify the three fundamental forces of nature - electromagnetism, strong nuclear force, and weak nuclear force - into a single force. SUSY (Supersymmetry) is a proposed extension of the Standard Model of particle physics, which predicts the existence of new particles that could help explain the unification of these forces. GUT and SUSY are often studied together as they both aim to address some of the unanswered questions in particle physics.

2. Can GUT exist without SUSY?

Yes, it is possible for GUT to exist without SUSY. In fact, there are several GUT models that do not require the existence of supersymmetric particles. However, SUSY is still an important concept in GUT as it provides a possible solution to some of the issues that arise in GUT, such as the hierarchy problem.

3. Is there any evidence for GUT being physically wrong?

Currently, there is no concrete evidence that suggests GUT is physically wrong. However, there are still many unanswered questions and challenges that need to be addressed in order for GUT to be fully accepted as a valid theory. Some of these challenges include the lack of experimental evidence and the inability to reconcile GUT with the results of general relativity.

4. How can we test the validity of GUT without SUSY?

Even without SUSY, there are still ways to test the validity of GUT. One way is through experimental data from high-energy particle colliders, which can help confirm or rule out certain predictions made by GUT. Another way is through observations of astrophysical phenomena, such as cosmic rays, which can provide insights into the fundamental forces at play in the universe.

5. Can GUT and SUSY ever be proven or disproven?

As with any scientific theory, it is not possible to prove or disprove GUT and SUSY with absolute certainty. However, as more experimental data is collected and analyzed, we can gain a better understanding of the validity of these theories. It is also possible that future discoveries or advancements in technology may provide new evidence that could support or contradict GUT and SUSY.

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