Approximate semi-amenability of Banach algebras

M. Shams Kojanaghi, K. Haghnejad Azar, M. R. Mardanbeigi

Published 2019-09-11Version 1

Let $\mathfrak{A}$ be a Banach algebra, and $\mathcal{X}$ a Banach $\mathfrak{A}$-bimodule. A bounded linear mapping $\mathcal{D}:\mathfrak{A}\rightarrow \mathcal{X}$ is approximately semi-inner derivation if there eixist nets $(\xi_{\alpha})_{\alpha}$ and $(\mu_{\alpha})_{\alpha}$ in $\mathcal{X}$ suh that, for each $a\in\mathfrak{A}$, $\mathcal{D}(a)=\lim_{\alpha}(a.\xi_{\alpha}-\mu_{\alpha}.a)$. $\mathfrak{A}$ is called approximately semi-amenable if for every Banach $\mathfrak{A}$-bimodule $\mathcal{X}$, every $\mathcal{D}\in\mathcal{Z}^{1}(\mathfrak{A},\mathcal{X}^{*})$ is approximtely semi-inner. There are some Banach algebras which are approximately semi-amenable, but not approximately amenable. In this manuscript, we investigate some properties of approximate semi-amenability of Banach algebras. Also in Theorem \ref{ee} we prove the approximate semi-amenability of Segal algebras on a locally compact, SIN group $G$.