An $n \times n$-matrix $U \in Mat(n, \mathbb{C})$ with entries in the complex numbers (for $n$ a natural number) is unitary if the following equivalent conditions hold
it preserves the canonical inner product on $\mathbb{C}^n$;
the operation $(-)^\dagger$ of transposing it and then applying complex conjugation to all its entries takes it to its inverse:
For fixed $n$, the unitary matrices under matrix product form a Lie group: the unitary group $\mathrm{U}(n)$ (or other notations).
Last revised on January 22, 2013 at 14:57:18. See the history of this page for a list of all contributions to it.