1302.0669 (Takaaki Hashimoto et al.)

Quantization of hypercharge in gauge groups locally isomorphic but
globally non-isomorphic to SU(3)_c X SU(2)_L X U(1)_Y    [PDF]

Takaaki Hashimoto, Mamoru Matsunaga, Kenta Yamamoto

In the Standard Model the hypercharges of quarks and leptons are not determined by the gauge group itself. In a recent paper [C. Hattori et al. Phys. Rev. D83, 015009 (2011)] it is shown that, if the direct product gauge group G_SM are slightly modified to the semidirect product group G'_SM, hypercharges are restricted to quantized values as n/6 mod Z (n = 0,1,3,4). In this Brief Report, we examine all of the compact Lie groups locally isomorphic to G_SM, and show G'_SM (or its isomorphisms) is the unique possibility that yields the correct hypercharge quantization.

View original: http://arxiv.org/abs/1302.0669