부산대학교 도서관

We investigate properties of essential spectra of disjointness preserving operators acting on Banach C(K)-modules. In particular, we prove that under some very mild conditions the upper semi-Fredholm spectrum of such an operator is rotation invariant. In the last part of the paper we provide a full description of the spectrum and the essential spectra of operators acting on Kaplansky modules of the form T = w U , where w ∈ C (K) , U is a d-isomorphism, and the spectrum of U is a subset of the unit circle. [ABSTRACT FROM AUTHOR]