Well working with the dynkin diagram of SU(5), one can easily see (by Dynkin's rule) that possible choices of SU(5) spontaneous symmetry breaking could be:(adsbygoogle = window.adsbygoogle || []).push({});

[itex] SU(5)→ SU(4) \times U(1) [/itex] I call the broken group [itex]G[/itex]

and

[itex] SU(5)→ SU(3) \times SU(2) \times U(1) [/itex] which I call [itex]SM[/itex]

So I have a question. Apart from the natural imposition of the [itex]SM[/itex] subgroup (since we know that this is the gauge symmetry of our below GUT scale physics) is there any particular way the nature could have chosen it to [itex]G[/itex]?

If you understood the question so far, don't procceed I'll try to make it clearer. I would expect that both G and SM are equally possible candidates, but something must have been there to choose the Standard Model to G... what is that something?

Thanks

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# SU(5) subgroups

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