A study of Schur multipliers and some Banach spaces of infinite matrices

Sammanfattning: This PhD thesis consists of an introduction and five papers, which deal with some spaces of infinite matrices and Schur multipliers. In the introduction we give an overview of the area that serves as a frame for  the rest of the Thesis. In Paper 1 we introduce the space $B_w(ell^2)$ of linear (unbounded) operators on $ell^2$ which map decreasing sequences from $ell^2$ into sequences from $ell^2$ and we find some classes of operators belonging either to $B_w(ell^2)$ or to the space of all Schur multipliers on $B_w(ell^2)$. In Paper 2 we further continue the study of the space $B_w(ell^p)$ in the range $1 In Paper 3 we prove a new characterization of the Bergman-Schatten spaces $L_a^p(D,ell^2)$, the space of all upper triangular matrices such that $|A(cdot)|_{L^p(D,ell^2)}