aequationes mathematicae

, Volume 42, Issue 1, pp 220–224

Unitary similarity of projectors


  • Dragomir Ž Doković
    • Department of Pure MathematicsUniversity of Waterloo
Research Papers

DOI: 10.1007/BF01818492

Cite this article as:
Doković, D.Ž. Aeq. Math. (1991) 42: 220. doi:10.1007/BF01818492


We deal with linear operators acting in a finite dimensional complex Hilbert space. We show that there exists a simple canonical form for projectors (not necessarily orthogonal) under unitary similarity. As a consequence we obtain a simple test for unitary similarity of projectors. IfP is a projector we show thatP andP * are unitarily similar. We also determine the isomorphism type of the algebra generated by the projectorsP andP *.

AMS (1980) subject classification

Primary 15A21, 15A30 Secondary 15A72, 15A18

Copyright information

© Birkhäuser Verlag 1991