Fréchet and (LB) sequence spaces induced by dual Banach spaces of discrete Cesàro spaces

The Fréchet (resp.\ (LB)) sequence spaces $ces(p+) := \cap_{r > p} ces(r), 1 \leq p < \infty$ (resp.\ $ces (p-) := \cup_{ 1 < r < p} ces (r), 1 < p \leq \infty),$ are known to be very different to the classical sequence spaces $\ell_ {p+}$ (resp., $\ell_{p_{-}}).$ Both of these classes of non-normable spaces $ces (p+), ces (p-)$ are defined via the family of reflexive Banach sequence spaces $ces (p), 1 < p < \infty .$ The dual Banach spaces $d (q), 1 < q < \infty ,$ of the discrete Cesàro spaces $ces (p), 1 < p < \infty,$ were studied by G.\ Bennett, A.\ Jagers and others. Our aim is to investigate in detail the corresponding sequence spaces $d (p+)$ and $d (p-),$ which have not been considered before. Some of their properties have similarities with those of $ces (p+), ces (p-)$ but, they also exhibit differences. For instance, $ces (p+)$ is isomorphic to a power series Fréchet space of order 1, whereas $d (p+)$ is isomorphic to such a space of infinite order. Every space $ces (p+), ces (p-)$ admits an absolute basis but, none of the spaces $d (p+), d (p-)$ have any absolute basis.

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