Published online by Cambridge University Press: 20 November 2018
J. Elton used an application of Ramsey theory to show that if $X$ is an infinite dimensional Banach space, then
${{c}_{0}}$
embeds in
$X$,
${{\ell }_{1}}$
embeds in
$X$, or there is a subspace of
$X$ that fails to have the Dunford–Pettis property. Bessaga and Pelczynski showed that if
${{c}_{0}}$
embeds in
${{X}^{*}}$
, then
${{\ell }_{\infty }}$
embeds in
${{X}^{*}}.$ Emmanuele and John showed that if
${{c}_{0}}$ embeds in
$K\left( X,\,Y \right)$, then
$K\left( X,\,Y \right)$ is not complemented in
$L\left( X,\,Y \right)$. Classical results from Schauder basis theory are used in a study of Dunford–Pettis sets and strong Dunford–Pettis sets to extend each of the preceding theorems. The space
${{L}_{{{w}^{*}}}}\left( {{X}^{*}},\,Y \right)$ of
${{w}^{*}}\,-\,w$ continuous operators is also studied.