4 papers
Lower bounds in -rational approximation to Blaschke products
Laurent Baratchart, Alexander Borichev, Sylvain Chevillard +2
We derive lower bounds in best rational approximation of given degree to finite Blaschke products, in the Hardy space of the unit disk. We first consider approximation to $z^…
Exponential stability of linear periodic difference-delay equations
Laurent Baratchart, Sébastien Fueyo, Jean-Baptiste Pomet
This paper deals with the stability of linear periodic difference delay systems, where the value at time of a solution is a linear combination with periodic coefficients of its…
Integral representation formula for linear non-autonomous difference-delay equations
Laurent Baratchart, Sébastien Fueyo, Jean-Baptiste Pomet
This note states and proves an integral representation formula of the ``variation-of-constant'' type for continuous solutions of linear non-autonomous difference delay systems, in…
n-th Root Optimal Rational Approximants to Functions with Polar Singular Set
L. Baratchart, H. Stahl, M. Yattselev
Let be a bounded Jordan domain and be its complement on the Riemann sphere. We investigate the -th root asymptotic behavior in of best rational approximants,…