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.
|Original language||English (US)|
|Journal||Journal of Mathematical Analysis and Applications|
|State||Published - Sep 15 2020|
All Science Journal Classification (ASJC) codes
- Applied Mathematics