Polar decomposition of an invertible complex matrix (source code)

= Polar decomposition of an invertible complex matrix

Every invertible complex matrix has the unique polar decomposition
$$
M=PU,
\qquad
P=\sqrt{MM^*},
\qquad
U=P^{-1}M,
$$
where $P$ is a positive-definite <Hermitian matrix> and $U$ is a <unitary matrix>. Writing $P=e^B$ gives $B=\frac12\log(MM^*)$, which is Hermitian.