Volume 31 • Number 2 • 2008   • On the Spectra of Some Non-Normal Operators M. H. M. Rashid, M. S. M. Noorani and A. S. Saari Abstract. In this paper, we prove the following:   (1) If T is invertible ω-hyponormal completely non-normal, then the point spectrum is empty.   (2) If T1 and T2 are injective ω-hyponormal and if T and S are quasisimilar,        then they have the same spectra and essential spectra.   (3) If T is (p,k)-quasihyponormal operator, then σjp (T)- {0} = σap (T)- {0} .   (4) If T ∗, S ∈ Β(Η) are injective (p, k)-quasihyponormal operator, and if       XT = SX, where X ∈ Β(Η) is an invertible, then there exists a unitary       operator U such that UT = SU and hence T and S are normal operators. 2000 Mathematics Subject Classification: 47A10, 47B20. Full text: PDF