On biunimodular vectors for unitary matrices

Hartmut Führ, Ziemowit Rzeszotnik

A biunimodular vector of a unitary matrix $A\in U(n)$ is a vector $v \in \mathbb{T}^n\subset\bc^n$ such that $Av\in {\mathbb{T}}^n$ as well. Over the last 30 years, the sets of biu…