i need what we mean by B-L extension of the Standard Model ?
A extension where Baryon and Lepton numbers make a prominent rule. In such extensions, the difference between Baryon Number and Lepton Number is recognized as a preserved quantity, and then promoted to some generator of the gauge group. This should be to extend the SU(3) colour group to SU(3)xU(1) or to SU(4)
Do not confuse with L-R extensions, for Left-Right, where SU(2)xU(1) is extended to SU(2)xSU(2).
The simultaneus use of both extensions, from SU(3)xSU(2)xU(1) to SU(4)xSU(2)xSU(2) is a very important model. Baez and Huerta like to show an "square" where SO(1O) can descent either into SU(4)xSU(2)xS(2) or to SU(5), and both of them can go down to SU(3)xSU(2)xU(1). Nice thing.
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