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JOURNALS // Matematicheskii Sbornik // Archive

Mat. Sb., 2021 Volume 212, Number 11, Pages 128–164 (Mi sm9024)

This article is cited in 1 paper

Convergence of two-point Padé approximants to piecewise holomorphic functions

M. L. Yattselevab

a Department of Mathematical Sciences, Indiana University – Purdue University Indianapolis, Indianapolis, IN, USA
b Keldysh Institute of Applied Mathematics of Russian Academy of Sciences, Moscow, Russia

Abstract: Let $f_0$ and $f_\infty$ be formal power series at the origin and infinity, and $P_n/Q_n$, $\deg(P_n),\deg(Q_n)\leq n$, be the rational function that simultaneously interpolates $f_0$ at the origin with order $n$ and $f_\infty$ at infinity with order ${n+1}$. When germs $f_0$ and $f_\infty$ represent multi-valued functions with finitely many branch points, it was shown by Buslaev that there exists a unique compact set $F$ in the complement of which the approximants converge in capacity to the approximated functions. The set $F$ may or may not separate the plane. We study uniform convergence of the approximants for the geometrically simplest sets $F$ that do separate the plane.
Bibliography: 26 titles.

Keywords: two-point Padé approximants, non-Hermitian orthogonality, strong asymptotics, $S$-contours, matrix Riemann-Hilbert approach.

UDC: 517.53

MSC: 42C05, 41A20, 41A21

Received: 24.10.2017 and 27.04.2021

DOI: 10.4213/sm9024


 English version:
Sbornik: Mathematics, 2021, 212:11, 1626–1659

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© Steklov Math. Inst. of RAS, 2026