SU(2) matrix
= SU(2) matrix
{c}
{title2=$U^\dagger U=I,\quad\det U=1$}
An SU(2) matrix is a two-by-two complex <unitary matrix> with <determinant> one. It has the form $\begin{pmatrix}a&b\\-\bar b&\bar a\end{pmatrix}$ with $|a|^2+|b|^2=1$. Its action on the <Riemann sphere> is a rotational <Möbius transformation>; opposite matrices induce the same sphere rotation.