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sweetser

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The gauge symmetry of the standard model is written in authoritative places like wikipedia :-) as U(1)xSU(2)xSU(3). This would have 12 elements in its Lie algebra corresponding to one photon, W+, W- and W0 or Z, and the 8 gluons. I recall reading discussions that such a characterization is not exactly right. U(1) is a subgroup of SU(2), and SU(2) is a subgroup of SU(3). My vague memory is recalling something like a "flag" must be added to U(1) so that it is nicely separated from SU(2), which also needs one of these flags or markers.

If someone in the know could fill me in, it will be appreciated as an hour of Googling did not turn up this detail of the standard model.

Thanks,

Doug