About the convergence rate Hermite – Pade approximants of exponential functions
| Autor: | Starovoitov, Alexander Pavlovich, Kechko, Elena P. |
|---|---|
| Jazyk: | English<br />Russian |
| Rok vydání: | 2021 |
| Předmět: | |
| Zdroj: | Известия Саратовского университета. Новая серия. Серия Математика. Механика. Информатика, Vol 21, Iss 2, Pp 162-172 (2021) |
| Druh dokumentu: | article |
| ISSN: | 1816-9791 2541-9005 |
| DOI: | 10.18500/1816-9791-2021-21-2-162-172 |
| Popis: | This paper studies uniform convergence rate of Hermite\,--\,Pad\'e approximants (simultaneous Pad\'e approximants) $\{\pi^j_{n,\overrightarrow{m}}(z)\}_{j=1}^k$ for a system of exponential functions $\{e^{\lambda_jz}\}_{j=1}^k$, where $\{\lambda_j\}_{j=1}^k$ are different nonzero complex numbers. In the general case a research of the asymptotic properties of Hermite\,--\,Pad\'e approximants is a rather complicated problem. This is due to the fact that in their study mainly asymptotic methods are used, in particular, the saddle-point method. An important phase in the application of this method is to find a special saddle contour (the Cauchy integral theorem allows to choose an integration contour rather arbitrarily), according to which integration should be carried out. Moreover, as a rule, one has to repy only on intuition. In this paper, we propose a new method to studying the asymptotic properties of Hermite\,--\,Pad\'e approximants, that is based on the Taylor theorem and heuristic considerations underlying the Laplace and saddle-point methods, as well as on the multidimensional analogue of the Van Rossum identity that we obtained. The proved theorems complement and generalize the known results by other authors. |
| Databáze: | Directory of Open Access Journals |
| Externí odkaz: |
|