k-Matrix

A $k$-matrix is a kind of Cube Root of the Identity Matrix defined by

$${\hbox{\sf k}} =\left[{\matrix{ 0 & 0 & -i\cr i & 0 & 0\cr 0 & 1 & 0\cr}}\right].$$

It satisfies

$${\hbox{\sf k}}^3={\hbox{\sf I}},$$

where I is the Identity Matrix.

See also Cube Root, Quaternion