Melnichenko, G. Structure of certain operators from a nest algebra. (English. Russian original) Zbl 0573.47040 Lith. Math. J. 22, 408-416 (1983); translation from Litov. Mat. Sb. 22, No. 4, 98-108 (1982). Let \({\mathcal L}(H)\) denote the algebra of all bounded linear operators on a complex Hilbert space H and let \(A\in {\mathcal L}(H)\) be similar to a self- adjoint operator Encyclopedia of Mathematics nLab Wikipedia . Then A gives rise in a natural way to a complete chain \({\mathcal G}\) of orthogonal projections Encyclopedia of Mathematics nLab Wikipedia Wikipedia Wolfram MathWorld Wolfram MathWorld on H and A belongs to the corresponding nest algebra Wikipedia Wolfram MathWorld \({\mathcal N}\). The main aim of the present note is to obtain the decomposition \(A=A_ 0+A_+\), where the selfadjoint operator Encyclopedia of Mathematics nLab Wikipedia \(A_ 0\) belongs to the von-Neumann algebra generated by \({\mathcal G}\) and \(A_+\) lies in the radical of \({\mathcal N}\). A corresponding multiplicative decomposition for an operator similar to a unitary one is also given. The paper ends with a proof of the existence of a conditional expectation nLab Wikipedia of \({\mathcal L}(H)\) onto the diagonal of an arbitrary nest algebra on H. Reviewer: T.A.Gillespie MSC: 47L30 Abstract operator algebras on Hilbert spaces 47B15 Hermitian and normal operators (spectral measures, functional calculus, etc.) 47A15 Invariant subspaces of linear operators 47C15 Linear operators in \(C^*\)- or von Neumann algebras Keywords:similar to a self-adjoint operator; nest algebra; von-Neumann algebra; radical; multiplicative decomposition; conditional expectation × Cite Format Result Cite Review PDF Full Text: DOI References: [1] M. S. Brodskii, Triangular and Jordan Representations of Linear Operators [in Russian], Nauka, Moscow (1969). [2] I. R. Ringrose, ”On some algebras of operators,” Proc. London Math. Soc., (3),15, No. 1, 61–83 (1965). · Zbl 0135.16804 · doi:10.1112/plms/s3-15.1.61 [3] I. Ts. Gokhberg and M. G. Krein, ”Description of contraction operators similar to unitary ones,” Funkts. Anal.,1, 38–60 (1967). · Zbl 0161.11601 [4] V. M. Brodskii, I. Ts. Gokhberg, and M. G. Krein, ”General theorems on triangular representations of linear operators and multiplicative representations of their characteristic functions,” Funkts. Anal.,3, No. 4, 1–27 (1969). · Zbl 0169.17401 · doi:10.1016/0022-1236(69)90048-2 [5] M. A. Naimark, Normed Rings [in Russian], Nauka, Moscow (1968). [6] I. A. Erdos and W. E. Longstaff, ”The convergence of triangular operators on Hilbert space,” Indiana Univ. Math. J.,22, No. 10, 929–938 (1973). · doi:10.1512/iumj.1973.22.22077 [7] I. R. Ringrose, ”Superdiagonal forms for compact linear operators,” Proc. London Math. Soc., (3),12, No. 46, 367–384 (1962). · Zbl 0102.10301 · doi:10.1112/plms/s3-12.1.367 [8] W. Arveson, ”Analyticity in operator algebras,” Am. J. Math., 89, No. 3, 578–642 (1967). · Zbl 0183.42501 · doi:10.2307/2373237 [9] K. Yosida, Functional Analysis [Russian translation], Mir, Moscow (1967). · Zbl 0152.32102 This reference list is based on information provided by the publisher or from digital mathematics libraries. Its items are heuristically matched to zbMATH identifiers and may contain data conversion errors. In some cases that data have been complemented/enhanced by data from zbMATH Open. This attempts to reflect the references listed in the original paper as accurately as possible without claiming completeness or a perfect matching.