The role of the algebraic structure in Wold-type decomposition

2021 ◽  
Vol 33 (4) ◽  
pp. 1033-1049
Author(s):  
G. A. Bagheri Bardi ◽  
Zbigniew Burdak ◽  
Akram Elyaspour
Keyword(s):  
Linear Algebra ◽  
Algebraic Structure ◽  
Von Neumann Algebras ◽  
Algebraic Approach ◽  
Von Neumann ◽  
Weak Operator ◽  
Commuting Pairs ◽  
Decomposition Theorems ◽  
Type Decomposition

Abstract In recent works [G. A. Bagheri-Bardi, A. Elyaspour and G. H. Esslamzadeh, Wold-type decompositions in Baer ∗ \ast -rings, Linear Algebra Appl. 539 2018, 117–133] and [G. A. Bagheri-Bardi, A. Elyaspour and G. H. Esslamzadeh, The role of algebraic structure in the invariant subspace theory, Linear Algebra Appl. 583 2019, 102–118], the algebraic analogues of the three major decomposition theorems of Wold, Nagy–Foiaş–Langer and Halmos–Wallen were established in the larger category of Baer * {*} -rings. The results have their versions for commuting pairs in von Neumann algebras. In the corresponding proofs, both norm and weak operator topologies are heavily involved. In this work, ignoring topological structures, we give an algebraic approach to obtain them in Baer * {*} -rings.

Type Decomposition and the Rectangular AFD Property for W*-TRO’s

2004 ◽  
Vol 56 (4) ◽  
pp. 843-870 ◽  
Author(s):  
Zhong-Jin Ruan
Keyword(s):  
Von Neumann Algebra ◽  
Von Neumann Algebras ◽  
Operator Space ◽  
Dual Operator ◽  
Von Neumann ◽  
Direct Sum ◽  
Cardinal Numbers ◽  
Finite Dimensional ◽  
Dimensional Property ◽  
Type Decomposition

AbstractWe study the type decomposition and the rectangular AFD property for W*-TRO’s. Like von Neumann algebras, every W*-TRO can be uniquely decomposed into the direct sum of W*- TRO's of type I, type II, and type III. We may further considerW*-TRO's of type Im,n with cardinal numbers m and n, and considerW*-TRO's of type IIλ,μ with λ, μ = 1 or ∞. It is shown that every separable stable W*-TRO (which includes type I∞, ∞, type II∞, ∞ and type III) is TRO-isomorphic to a von Neumann algebra. We also introduce the rectangular version of the approximately finite dimensional property for W*-TRO’s. One of our major results is to show that a separable W*-TRO is injective if and only if it is rectangularly approximately finite dimensional. As a consequence of this result, we show that a dual operator space is injective if and only if its operator predual is a rigid rectangular space (equivalently, a rectangular space).

Weakly Compact, Operator-Valued Derivations of Type I Von Neumann Algebras

1984 ◽  
Vol 36 (3) ◽  
pp. 436-457
Author(s):  
Steve Wright
Keyword(s):  
Von Neumann Algebras ◽  
Linear Operators ◽  
Type I ◽  
Weakly Compact ◽  
Bounded Linear ◽  
Von Neumann ◽  
Weakly Compact Operator ◽  
Weak Operator ◽  
Image Position ◽  
Compact Extension

In [18], the author initiated an investigation of compact, Banach-module-valued derivations of C*-algebras. In collaboration with C. A. Akemann [3] and S.-K. Tsui [16], he determined the structure of all compact and weakly compact, A-valued derivations of a C*-algebra A, and of all compact, B(H)-valued derivations of a C*-subalgebra of B(H), the algebra of bounded linear operators on a Hilbert space H. In this paper, we begin the study of weakly compact, B(H)-valued derivations of C*-subalgebras of B(H).Let R be a C*-subalgebra of B(H), δ:R → B(H) a weakly compact derivation, i.e., a weakly compact linear map which hasSince δ has a unique weakly compact extension to a derivation of the closure of R in the weak operator topology (WOT) on B(H) (consult the proof of Theorem 3.1 of [16]), we may assume with no loss of generality that R is a von Neumann subalgebra of B(H). In this paper, we determine in Lemma 4.1 and Theorems 4.3 and 4.10 the structure of δ when R is type I, using I. E. Segal's multiplicity theory [14] for type I von Neumann algebras and results of E. Christensen [6], [7] on B(H)-valued derivations of von Neumann algebras.

Correspondences and Approximation Properties for von Neumann Algebras

2003 ◽  
Vol 14 (06) ◽  
pp. 619-665 ◽  
Author(s):  
Jon Kraus
Keyword(s):  
Approximation Property ◽  
Von Neumann Algebras ◽  
Locally Compact Groups ◽  
Compact Groups ◽  
Approximation Properties ◽  
Locally Compact ◽  
Von Neumann ◽  
Weak Amenability ◽  
Operator Approximation ◽  
Weak Operator

The notion of the amenability of a locally compact group has been extended in various ways. Two weaker versions of amenability, weak amenability and the approximation property, have been defined for locally compact groups (by Haagerup and Haagerup and Kraus, respectively) and Bekka has defined a notion of amenability for representations of locally compact groups. Correspondences can be viewed as a generalization of representations of such groups. Using this viewpoint, Ananthraman–Delaroche has defined a notion of (left) amenability for correspondences. In this paper, we define notions of weak amenability and the approximation property for correspondences (and representations of locally compact groups), and obtain various results concerning these notions. Ananthraman–Delaroche showed that if N ⊂ M is an inclusion of von Neumann algebras, and if the associated inclusion correspondence is left amenable, then various approximation properties of N (semidiscreteness, the weak* completely bounded approximation property, and the weak* operator approximation property) are shared by M. We show that if this correspondence has the (weaker) approximation property, then if N has the weak* operator approximation property, so does M. An application of this result to crossed products is also given.

Banach–Mazur stability of von Neumann algebras

2020 ◽  
pp. 1-26
Author(s):  
Jean Roydor
Keyword(s):  
Von Neumann Algebra ◽  
Hochschild Cohomology ◽  
Von Neumann Algebras ◽  
Cohomology Groups ◽  
Von Neumann ◽  
Type Decomposition

We initiate the study of perturbation of von Neumann algebras relatively to the Banach–Mazur distance. We first prove that the type decomposition is continuous, i.e. if two von Neumann algebras are close, then their respective summands of each type are close. We then prove that, under some vanishing conditions on its Hochschild cohomology groups, a von Neumann algebra is Banach–Mazur stable, i.e. any von Neumann algebra which is close enough is actually Jordan ∗-isomorphic. These vanishing conditions are possibly empty.

scholarly journals Type decomposition in posets

2016 ◽  
Vol 66 (5) ◽  
Author(s):  
Tristan Bice
Keyword(s):  
Von Neumann Algebras ◽  
Classical Type ◽  
Von Neumann ◽  
Decomposition Theory ◽  
Type Decomposition

AbstractMotivated by the classical type decomposition of von Neumann algebras, and various more recent extensions to other structures, we develop a type decomposition theory for general posets.

Lectures on von Neumann Algebras

2019 ◽  
Author(s):  
Serban-Valentin Stratila ◽  
Laszlo Zsido
Keyword(s):  
Von Neumann Algebras ◽  
Von Neumann
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