Abstract :
The class of σ-regular matrices was defined and characterized by Schaefer [P. Schaefer, Infinite matrices
and invariant means, Proc. Amer. Math. Soc. 36 (1972) 104–110] and further studied by Mursaleen [Mursaleen,
On some new invariant matrix methods of summability, Quart. J. Math. Oxford 34 (1983) 77–86],
Ahmad and Mursaleen [Z.U. Ahmad, Mursaleen, An application of Banach limits, Proc. Amer. Math. Soc.
103 (1988) 244–246]. In this paper we characterize four-dimensional σ-multiplicative matrices, and establish
a core theorem.
© 2006 Elsevier Inc. All rights reserved.
