In this article, we study characterization, stability, and spectral mapping the- orem for Browder＇s essential spectrum, Browder＇s essential defect spectrum and Browder＇s essential approximate point spectrum of clos...In this article, we study characterization, stability, and spectral mapping the- orem for Browder＇s essential spectrum, Browder＇s essential defect spectrum and Browder＇s essential approximate point spectrum of closed densely defined linear operators on Banach spaces.展开更多
An operator T is said to be paranormal if ｜｜T^2 x ｜｜ 〉｜｜Tx｜｜^2 holds for every unit vector x. Several extensions of paranormal operators are considered until now, for example absolute-k-paranormal and p-paran...An operator T is said to be paranormal if ｜｜T^2 x ｜｜ 〉｜｜Tx｜｜^2 holds for every unit vector x. Several extensions of paranormal operators are considered until now, for example absolute-k-paranormal and p-paranormal introduced in [10], [14], respectively. Yamazaki and Yanagida [38] introduced the class of absolute-（p, r）-paranormal operators as a further generalization of the classes of both absolute-k-paranormal and p-paranormal operators. An operator T ∈ B（H） is called absolute-（p, r）-paranormal operator if ｜｜｜T｜p｜T^＊ ｜^rx｜｜^r 〉 ｜｜｜T^＊｜^rx｜｜p＋r for every unit vector x ∈ H and for positive real numbers p 〉 0 and r 〉 0. The famous result of Browder, that self adjoint operators satisfy Browder＇s theorem, is extended to several classes of operators. In this paper we show that for any absolute-（p, r）- paranormal operator T, T satisfies Browder＇s theorem and a-Browder＇s theorem. It is also shown that if E is the Riesz idempotent for a nonzero isolated point μ of the spectrum of a absolute-（p, r）-paranormal operator T, then E is self-adjoint if and only if the null space of T -μ, N（T - μ） N（T^＊ - ^μ）.展开更多
文摘In this article, we study characterization, stability, and spectral mapping the- orem for Browder＇s essential spectrum, Browder＇s essential defect spectrum and Browder＇s essential approximate point spectrum of closed densely defined linear operators on Banach spaces.
基金supported by Taibah University Research Center Project(1433/803)
文摘An operator T is said to be paranormal if ｜｜T^2 x ｜｜ 〉｜｜Tx｜｜^2 holds for every unit vector x. Several extensions of paranormal operators are considered until now, for example absolute-k-paranormal and p-paranormal introduced in [10], [14], respectively. Yamazaki and Yanagida [38] introduced the class of absolute-（p, r）-paranormal operators as a further generalization of the classes of both absolute-k-paranormal and p-paranormal operators. An operator T ∈ B（H） is called absolute-（p, r）-paranormal operator if ｜｜｜T｜p｜T^＊ ｜^rx｜｜^r 〉 ｜｜｜T^＊｜^rx｜｜p＋r for every unit vector x ∈ H and for positive real numbers p 〉 0 and r 〉 0. The famous result of Browder, that self adjoint operators satisfy Browder＇s theorem, is extended to several classes of operators. In this paper we show that for any absolute-（p, r）- paranormal operator T, T satisfies Browder＇s theorem and a-Browder＇s theorem. It is also shown that if E is the Riesz idempotent for a nonzero isolated point μ of the spectrum of a absolute-（p, r）-paranormal operator T, then E is self-adjoint if and only if the null space of T -μ, N（T - μ） N（T^＊ - ^μ）.
