[[Mod. note -- I have "repaired" various non-ASCII characters as best(adsbygoogle = window.adsbygoogle || []).push({});

as I can, but it's *much* safer if postings are submitted in 7-bit-ASCII

only. In particular, Microsoft Windows "smart quotes" tend to get

quite mangled before they arrive at s.p.r moderstors' mailboxes... :(

-- jt]]

In the SU(5) grand unified theory, there are two sets of Higgs fields.

They are the {5} and {24} representations (we don't consider {45}

here). {24} breaks SU(5) down to SU(3)c*SU(2)l*U(1)y, and gives mass

to X gauge bosons via Higgs mechanism. {5} breaks SU(3)c*SU(2)l*U(1)y

further down to SU(3)c*U(1)em, and gives mass to W+- and Z gauge

bosons.

However, only {5} gives mass directly to the fermions via a Yukawa

type coupling. The conventional wisdom is that the "Higgs

representation must appear in the tensor product of the SU(5)

representations in which the fermion and its antifermion

appear." (H.Georgi's Lie Algebras in Particle Physics, Page 234-235).

This reasoning sounds empirical to me, because it's based on the way

fermion and its antifermion are assigned to different representations

of SU(5). Is there any first principle which explains why {24} is not

mass generating for fermions?

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# Question about Higgs fields in SU(5) GUT.

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