African Journal of
Mathematics and Computer Science Research

  • Abbreviation: Afr. J. Math. Comput. Sci. Res.
  • Language: English
  • ISSN: 2006-9731
  • DOI: 10.5897/AJMCSR
  • Start Year: 2008
  • Published Articles: 262

Short Communication

Invariance of numerical range under isometric transformation

A. W. Wafula* and J. M. Khalagai
University of Nairobi, School of Mathematics, P. O. Box 30197, Nairobi, Kenya.
Email: [email protected]

  •  Accepted: 27 October 2009
  •  Published: 28 February 2010

Abstract

In this paper, we look at some properties of isometries and conditions for a quasi-affinity to be unitary. Among other results it is proved that if A is a partial isometry such that either 0Ñ”W(A) or 0Ñ”W(An) for some positive integer n then A is unitary.

 

Key words: Numerical range and unitary operator.

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