Relations Between the Spectra of Semi-Hyponormal Operators and those of the General Polar Symbols
Daoxing Xia · Operator theory · 1983
In operator theory, to determine spectra of operators is the first question that one would like to settle. In the present chapter we shall make use of the general symbols (or the general polar symbols) to determine the spectra of hyponormal operators (respectively semi-hyponormal operators correspondingly). Since the general symbols are normal operators, and the general polar symbols of the operators in SHU are also normal and their models are quite simple, their spectra can be decided easily—we shall give a method in §1—so it is significant to determine spectra of nonnormal operators by that of the general symbols or general polar symbols.