Fredholm operators and essential S-spectrum in the quaternionic setting
Fredholm operators and essential S-spectrum in the quaternionic setting
For bounded right linear operators, in a right quaternionic Hilbert space with a left multiplication defined on it, we study the approximate $S$-point spectrum. In the same Hilbert space, then we study the Fredholm operators and the Fredholm index. In particular, we prove the invariance of the Fredholm index under …