Submatrices of four dimensional summability matrices

Abstract

In this paper, we show that a matrix that maps ℓ′′ into ℓ′′ can be obtained from any RH-regular matrix by the deletion of rows. Also a four dimensional conservative matrix can be obtained by the deletion of rows from a matrix that preserves boundedness. We will use these techniques to derive a sufficient condition for a four dimensional matrix to sum an unbounded sequence.