# Can B(l^p) ever be amenable?

Research paper by **Matthew Daws, Volker Runde**

Indexed on: **08 Jun '08**Published on: **08 Jun '08**Published in: **Mathematics - Functional Analysis**

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#### Abstract

It is known that ${\cal B}(\ell^p)$ is not amenable for $p =1,2,\infty$, but
whether or not ${\cal B}(\ell^p)$ is amenable for $p \in (1,\infty) \setminus
\{2 \}$ is an open problem. We show that, if ${\cal B}(\ell^p)$ is amenable for
$p \in (1,\infty)$, then so are $\ell^\infty({\cal B}(\ell^p))$ and
$\ell^\infty({\cal K}(\ell^p))$. Moreover, if $\ell^\infty({\cal K}(\ell^p))$
is amenable so is $\ell^\infty(\mathbb{I},{\cal K}(E))$ for any index set
$\mathbb I$ and for any infinite-dimensional ${\cal L}^p$-space $E$; in
particular, if $\ell^\infty({\cal K}(\ell^p))$ is amenable for $p \in
(1,\infty)$, then so is $\ell^\infty({\cal K}(\ell^p \oplus \ell^2))$. We show
that $\ell^\infty({\cal K}(\ell^p \oplus \ell^2))$ is not amenable for $p
=1,\infty$, but also that our methods fail us if $p \in (1,\infty)$. Finally,
for $p \in (1,2)$ and a free ultrafilter $\cal U$ over $\posints$, we exhibit a
closed left ideal of $({\cal K}(\ell^p))_{\cal U}$ lacking a right approximate
identity, but enjoying a certain, very weak complementation property.