On LR2-best rational approximants to Markov functions on several intervals

Abstract

Let f(z)=∫(z−x)−1dμ(x), where μ is a Borel measure supported on several subintervals of (−1,1) with smooth Radon–Nikodym derivative. We study strong asymptotic behavior of the error of approximation (f−rn)(z), where rn(z) is the LR2-best rational approximant to f(z) on the unit circle with n poles inside the unit disk.