Spectral mapping theorems and perturbation theorems for Browder’s essential spectrum
Spectral mapping theorems and perturbation theorems for Browder’s essential spectrum
If <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper T"> <mml:semantics> <mml:mi>T</mml:mi> <mml:annotation encoding="application/x-tex">T</mml:annotation> </mml:semantics> </mml:math> </inline-formula> is a closed, densely defined linear operator in a Banach space, F. E. Browder has defined the essential spectrum of <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper T comma e s s left-parenthesis upper T right-parenthesis"> <mml:semantics> <mml:mrow> …