For a rational matrix function Φ with poles outside the unit circle, we estimate the degree of the unique superoptimal approximation 𝒜Φ by matrix functions analytic in the unit disk. We obtain sharp ...

This is a preview. Log in through your library . Abstract Suppose that 2d - 2 tangent lines to the rational normal curve $z \mapsto (1 : z : ... : z^d)$ in d ...