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- Y. Choi
- 2008

We continue the investigation of notions of approximate amenability that were introduced in work of the second and third authors together with R. J. Loy. It is shown that every boundedly approximately contractible Banach algebra has a bounded approximate identity, and that the Fourier algebra of the free group on two generators is not operator approximately… (More)

We characterize those derivations from the convolution algebra l(Z+) to its dual which are weakly compact, providing explicit examples which are not compact. The characterization is combinatorial, in terms of “translation-finite” subsets of Z+, and we investigate how this notion relates to other notions of “smallness’ for infinite subsets of Z+. In… (More)

- Youn-Seo Choi, Byungchan Kim
- Eur. J. Comb.
- 2012

- Y Choi
- 2009

Let X be a Banach space on which a discrete group Γ acts by isometries. For certain natural choices of X, every element of the group algebra, when regarded as an operator on X, has empty residual spectrum. We show, for instance, that this occurs if X is l2(Γ) or the group von Neumann algebra VN(Γ). In our approach, we introduce the notion of a surjunctive… (More)

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