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Tauberian theorems for general power series methods

Published online by Cambridge University Press:  24 October 2008

R. Kiesel
Affiliation:
University of Ulm, Germany
U. Stadtmüller
Affiliation:
University of Ulm, Germany

Extract

Let us assume throughout that (pn) denotes a sequence of reals which satisfies

For real sequences (sn) with increments an = snsn−1 for n ≥ 0,(where s−1 = 0), we consider the power seriesmethod of summability (P), where we say

The power series methods (P) containthe so-called (Jp)-methods (R = 1)and the Borel-type methods (Bp)(R = ∞). We consider only regular (P)-methods, i.e. sns implies sns(P). By theorem 5 in [5], p.49, we have regularity if and only if

Here we are interested in the converse conclusion, namely sns(P) implies sns, which can only be validiffurther conditions, so-called Tauberian conditions are satisfied by (sn). These so-called Tauberian theorems for power series methods have a long history; see e.g. the books [5, 14, 23], and they found new attentionrecently in the papers [6, 18, 19, 20] and [8, 9, 10, 11, 12]. The latter papers contain certain o- Tauberian theorems for all power series methods in question and O-Tauberian theorems, if the weight sequence (pn) can be interpolated by alogarithmico-exponential function g(·)(see e.g. [4]), i.e.

Type
Research Article
Copyright
Copyright © Cambridge Philosophical Society 1991

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