Semi-Browder operators and perturbations
Vladimir Rakočević · Studia Mathematica · 1997
An operator in a Banach space is called upper (resp. lower) semi-Browder if it is upper (lower) semi-Fredholm and has a finite ascent (resp. descent). An operator in a Banach space is called semi-Browder if it is upper semi-Browder or lower semi-Browder.