The perturbation classes problem for subprojective and superprojective Banach spaces
arXiv:2006.05802 · doi:10.1016/j.jmaa.2020.124191
Abstract
We show that the perturbation class for the upper semi-Fredholm operators between two Banach spaces X and Y coincides with the strictly singular operators when X is subprojective and that the perturbation class for the lower semi-Fredholm operators coincides with the strictly cosingular operators when Y is superprojective. Similar results were previously obtained under stronger conditions for X and Y.
6 pages