Core theorems for subsequences of double complex sequences
The authors prove core theorems for double sequences with complex entries. These results extend the work of \textit{H. I. Miller} and \textit{R. F. Patterson} [Acta Math. Hung. 119, No. 1--2, 71--80 (2008; Zbl 1212.42021)] dealing with double sequences of real numbers. The authors give an answer to the question ``If \(w\) is a bounded double sequence with complex entries and \(A\) is a four-dimensional matrix summability method, under what conditions on \(A\) does there exist \(z\), a subsequence (rearrangement), of \(w\) such that each complex number \(t\) in the core of \(w\) is a limit point of \(Az\)?''.
scientific article; zbMATH DE number 5919209