English

Can B(l^p) ever be amenable?

Functional Analysis 2008-08-02 v3

Abstract

It is known that B(p){\cal B}(\ell^p) is not amenable for p=1,2,p =1,2,\infty, but whether or not B(p){\cal B}(\ell^p) is amenable for p(1,){2}p \in (1,\infty) \setminus \{2 \} is an open problem. We show that, if B(p){\cal B}(\ell^p) is amenable for p(1,)p \in (1,\infty), then so are (B(p))\ell^\infty({\cal B}(\ell^p)) and (K(p))\ell^\infty({\cal K}(\ell^p)). Moreover, if (K(p))\ell^\infty({\cal K}(\ell^p)) is amenable so is (I,K(E))\ell^\infty(\mathbb{I},{\cal K}(E)) for any index set I\mathbb I and for any infinite-dimensional Lp{\cal L}^p-space EE; in particular, if (K(p))\ell^\infty({\cal K}(\ell^p)) is amenable for p(1,)p \in (1,\infty), then so is (K(p2))\ell^\infty({\cal K}(\ell^p \oplus \ell^2)). We show that (K(p2))\ell^\infty({\cal K}(\ell^p \oplus \ell^2)) is not amenable for p=1,p =1,\infty, but also that our methods fail us if p(1,)p \in (1,\infty). Finally, for p(1,2)p \in (1,2) and a free ultrafilter U\cal U over \posints\posints, we exhibit a closed left ideal of (K(p))U({\cal K}(\ell^p))_{\cal U} lacking a right approximate identity, but enjoying a certain, very weak complementation property.

Keywords

Cite

@article{arxiv.0711.4311,
  title  = {Can B(l^p) ever be amenable?},
  author = {Matthew Daws and Volker Runde},
  journal= {arXiv preprint arXiv:0711.4311},
  year   = {2008}
}

Comments

25 pages; cleaned up

R2 v1 2026-06-21T09:47:51.535Z