New approach to a-Weyl's theorem and some preservation results (Q2047458)

In modern terminology, Weyl proved that the spectral points of a self-adjoint operator which do not belong to Weyl spectrum are precisely the eigenvalues of finite multiplicity which are isolated points of the spectrum. Many generalizations and variants have been proved by several authors. In this paper new spectral properties are introduced and investigated in connection with other Weyl type theorems. Among other things, it is proved that some of these spectral properties are equivalent and extend a classical theorem of Browder.