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Article
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The Quarterly Journal of Mathematics
Article . 1983 . Peer-reviewed
Data sources: Crossref
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ON SOME NEW INVARIANT MATRIX METHODS OF SUMMABILITY

On some new invariant matrix methods of summability
Authors: Mursaleen;

ON SOME NEW INVARIANT MATRIX METHODS OF SUMMABILITY

Abstract

Let \(\sigma\) be a mapping of the set of positive integers into itself. A continuous linear functional \(\phi\) on the space \(\ell^{\infty}\) of real bounded sequences is a \(\sigma\)-mean if \(\phi(x)\geq 0\) when the sequence \(x=(x_ n)\) has \(x_ n\geq 0\) for all n, \(\phi(e)=1\) where \(e:=(1,1,...)\), and \(\phi((x_{\sigma(n)}))=\phi(x)\) for all \(x\in \ell^{\infty}\). Let \(V_{\sigma}\) be the space of bounded sequences all of whose \(\sigma\)-means are equal, and let \(\sigma\)-lim x be the common value of all \(\sigma\)-means on x. In the special case in which \(\sigma(n):=n+1\) the \(\sigma\)-means are exactly the Banach-limits, and \(V_{\sigma}\) is the space of all almost convergent sequences considered by \textit{G. G. Lorentz} [Acta Math. 80, 167-190 (1948; Zbl 0031.29501)]. In a natural way the author of this paper introduces the space \(BV_{\sigma}\) of sequences of \(\sigma\)-bounded variation, which is a Banach space. Then he characterizes all real infinite matrices A, which are absolutely \(\sigma\)-conservative (absolute \(\sigma\)-regular). Thereby A is said to be absolutely \(\sigma\)-conservative if and only if \(Ax\in BV_{\sigma}\) for all \(x\in bv\), where bv denotes the space of sequences of bounded variation, and A is said to be absolutely \(\sigma\)-regular if and only if A is absolutely \(\sigma\)-conservative and \(\sigma -\lim Ax=\lim x\) for all \(x\in bv\).

Related Organizations
Keywords

Matrix methods for summability, invariant means, absolutely sigma-conservative matrices, inclusion theorems, General summability methods, almost convergence, sigma-convergence, sequences of sigma-bounded variation, Inclusion and equivalence theorems in summability theory

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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
69
Top 10%
Top 1%
Average
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