Standard Model anomaly cancellation
= Standard Model anomaly cancellation
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In each Standard Model generation, quark and lepton hypercharges cancel the $SU(3)_c^3$, $SU(3)_c^2U(1)_Y$, $SU(2)_L^2U(1)_Y$, $U(1)_Y^3$, and mixed gauge-gravitational anomalies. The four left-handed $SU(2)_L$ doublets also avoid the global Witten anomaly.