SpL(6)×UY(1)extension of the electroweak theory

The generation structure of quarks and leptons is incorporated with the electroweak theory in an ${\mathrm{Sp}}_L\mathrm{}\left(6\right)\mathrm{}\times {\mathrm{U}}_Y\mathrm{}\left(1\right)\mathrm{}$ model. In this model, the first-generation fermions are naturally light because their masses are generated only as two-loop corrections. Also the inequality $m_u<m_d$ is related to $m_t>m_b$.