Classification of essentially normal operators

Author(s):  
A. M. Davie
2008 ◽  
Vol 155 (6) ◽  
pp. 950-955
Author(s):  
V. Futorny ◽  
R. A. Horn ◽  
V. V. Sergeichuk

Author(s):  
C. R. Putnam

SynopsisLet T be a hyponormal operator on a Hilbert space, so that T*T – TT*≧ 0. Let T have the Cartesian representation T = H + iJ where H has the spectral family {Et} and suppose that EtJ − JEt is compact for almost all t on a Borei set α satisfying E(α) = I. The principal result (Theorem 3) is that under these hypotheses T must be normal. In case T is hyponormal and essentially normal some sufficient conditions are given assuring that, for a fixed t, EtJ − JEt is compact.


1990 ◽  
Vol 20 (2) ◽  
pp. 613-618
Author(s):  
L. WILLIAMS

Author(s):  
Kenneth R. Davidson

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