This is an announcement for the paper “Quotient algebra of compact-by-approximable operators on Banach spaces failing the approximation property” by Hans-Olav Tyllihttps://arxiv.org/search/math?searchtype=author&query=Tylli%2C+H, Henrik Wirzeniushttps://arxiv.org/search/math?searchtype=author&query=Wirzenius%2C+H.
Abstract: We initiate a study of structural properties of the quotient algebra $\mathcal K(X)/\mathcal A(X)$ of the compact-by-approximable operators on Banach spaces $X$ failing the approximation property. Our main results and examples include the following: (i) there is a linear isomorphic embedding from $c_0$ into $\mathcal K(Z)/\mathcal A(Z)$, where $Z$ belongs to the class of Banach spaces constructed by Willis that have the metric compact approximation property but fail the approximation property, (ii) there is a linear isomorphic embedding from a non-separable space $c_0(Γ)$ into $\mathcal K(Z_{FJ})/\mathcal A(Z_{FJ})$, where $Z_{FJ}$ is a universal compact factorisation space arising from the work of Johnson and Figiel.
The paper may be downloaded from the archive by web browser from URL https://arxiv.org/abs/1811.09402