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, Volume 54, Issue 3, pp 249–259 | Cite as

Formeln für Pole der Resolvente und den Radius eines wesentlichen Spektrums

  • Hans -Dieter Wacker


Let E be a complex Banach space and T a bounded linear operator. If σw(T) is the set of all spectral points of T which are not poles of the resolvent and rw(T) its radius, we give formulas for the moduli of all poles lying outside the circle with radius rw(T). We further prove that\(r_w (T) = \mathop {\lim }\limits_{k \to \infty } [\pi (T^k )]^{1/k} \), where π(T)=inf(∥T−F∥∶F(T−F)=(T−F)F=0,F∈F and F is the Caradus class of operators with rational resolvent. Finally we give an estimation of rw(S+T) and rw(S·T).


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Copyright information

© Springer-Verlag 1986

Authors and Affiliations

  • Hans -Dieter Wacker
    • 1
  1. 1.Mathematisches Institut IUniversität KarlsruheKarlsruhe

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