 Triality (SU(3))

The central element $\omega I$ of SU(3), with $\omega =e^{2\pi i/3}$, acts on an irreducible representation of Dynkin labels $(a,b)$ as ${\omega }^{a+2b}$. This residue is its triality. In a tensor realization the representation has $a+2b$ fundamental boxes, and a complete column of three is a singlet; removing such columns preserves the residue. Tensor products add trialities and complex conjugation reverses them.