Von Neumann equivalence and group exactness

We will show that group exactness is a von Neumann equivalence invariant. This result generalizes the previously known fact stating that group exactness is stable under measure equivalence and W*-equivalence.     

Multiplication operators defined by covering maps on the Bergman space: The connection between operator theory and von Neumann algebras

In this paper, we combine methods of complex analysis, operator theory and conformal geometry to construct a class of Type II factors in the theory of von Neumann algebras, which arise essentially from holomorphic coverings of bounded planar domains. One will see how types of such von Neumann algebras are related to algebraic topology of planar domains. As a result, the paper establishes a fascinating connections to one of the long-standing problems in free group factors. An interplay of analytical, geometrical, operator and group theoretical techniques is intrinsic to the paper.     

Von Neumann代数上P点ξ-Lie导子的刻画

设A是没有I_1型中心直和项的von Neumann代数,P∈A是一个非中心的空核投影且其中心包络是I.研究了Von Neumann代数上P点ξ-Lie导子δ,得到了对任意A∈A,存在T∈A使得δ(A)=AT-TA,这里非零数ξ∈F且ξ≠±1.     

On the double commutant of Cowen-Douglas operators

Let T be a Cowen-Douglas operator. In this paper, we study the von Neumann algebra V^?(T) consisting of operators commuting with both T and T^? from a geometric viewpoint. We identify operators in V^?(T) with connection-preserving bundle maps on E(T), the holomorphic Hermitian vector bundle associated to T. By studying such bundle maps, the structure of V^?(T) as well as information on reducing subspaces of T can be determined.     

保正交性或与|·|~k交换的可加映射

设H是复Hilbert空间,B（H）表示H上所有有界线性算子构成的代数.本文刻划了B（H）上保正交性的可加映射和von Neumann代数上与运算|·|k交换的可加映射.     

Continuity and generators of dynamical semigroups for infinite Bose systems

For a class of quasifree quantum dynamical semigroups on the algebra of the canonical commutation relations (CCR) we give sufficient conditions for these semigroups to extend to ultraweakly continuous semigroups of normal operators on the von Neumann algebra associated with a representation of the CCR. Then the explicit form of the generators of the extended semigroups is calculated.     

von Neumann代数上非线性强保交换映射

设M是作用在维数大于2的复可分Hilbert空间上的因子von_Neumann代数.本文证明了M上的每个非线性强保交换满射Φ都具有形式:存在常数λ∈{-1,1)和非线性函数h:M→C使得对任意A∈M,有Φ(A)=λA+h(A)I.     

The asymptotic lift of a completely positive map

Starting with a unit-preserving normal completely positive map acting on a von Neumann algebra—or more generally a dual operator system—we show that there is a unique reversible system (i.e., a complete order automorphism α of a dual operator system N) that captures all of the asymptotic behavior of L, called the asymptotic lift of L. This provides a noncommutative generalization of the Frobenius theorems that describe the asymptotic behavior of the sequence of powers of a stochastic n×n matrix. In cases where M is a von Neumann algebra, the asymptotic lift is shown to be a W^∗-dynamical system (N,Z), and we identify (N,Z) as the tail flow of the minimal dilation of L. We are also able to identify the Poisson boundary of L as the fixed algebra Nα. In general, we show the action of the asymptotic lift is trivial iff L is slowly oscillating in the sense that

     

Von Neumann代数中的套子代数

本文主要讨论因子Ｖｏｎ Ｎｅｕｍａｎｎ代数中套子代数上的线性满等距和自伴导子．证明了因子Ｖｏｎ Ｎｅｕｍａｎｎ代数中套子代数上的每个线性满等距是同构乘酉算子或者是反同构乘酉算子;给出了其上自伴导子是内导子的条件并得到有限因子 Ｖｏｎ Ｎｅｕｍａｎｎ代数中套子代数上的每个自伴导子都是内导子．     

Tent spaces associated with semigroups of operators

We study tent spaces on general measure spaces (Ω,μ). We assume that there exists a semigroup of positive operators on Lp(Ω,μ) satisfying a monotone property but do not assume any geometric/metric structure on Ω. The semigroup plays the same role as integrals on cones and cubes in Euclidean spaces. We then study BMO spaces on general measure spaces and get an analogue of Fefferman's H¹-BMO duality theory. We also get a H¹-BMO duality inequality without assuming the monotone property. All the results are proved in a more general setting, namely for noncommutative Lp spaces.     

Unitary Bases and Noncommutative Wavelets

In this paper, we construct new unitary bases in noncommutative wavelets.     

On the equations defining monomial curves

Let C be a monomial curve in three dimensional projective space over an algebraically closed field K of characteristic zero . We give several necessary criterions for C to be set theoretic complete intersection. Using these criterions we get several restrictions concerning the form of the equations that define C set theoretically.     

On Maximal Abelian Self-adjoint Subalgebras of Factors of Type Ⅱ1

In this note, we show that if N is a proper subfactor of a factor M of type Ⅱ1 with finite Jones index, then there is a maximal abelian self-adjoint subalgebra （masa） A of N that is not a masa in ,M. Popa showed that there is a proper subfactor R0 of the hyperfinite type Ⅱ1 factor R such that each masa in R0 is also a masa in R. We shall give a detailed proof of Popa＇s result.     

Tracial algebras and an embedding theorem

We prove that every positive trace on a countably generated ∗-algebra can be approximated by positive traces on algebras of generic matrices. This implies that every countably generated tracial ∗-algebra can be embedded into a metric ultraproduct of generic matrix algebras. As a particular consequence, every finite von Neumann algebra with separable pre-dual can be embedded into an ultraproduct of tracial ∗-algebras, which as ∗-algebras embed into a matrix-ring over a commutative algebra.     

Stopping times for quantum Markov chains

In the paper we introduce stopping times for quantum Markov states. We study algebras and maps corresponding to stopping times, give a condition of strong Markov property and give classification of projections for the property of accessibility. Our main result is a new recurrence criterium in terms of stopping times (Theorem 1 and Corollary 2). As an application of the criterium we study how, in Section 6, the quantum Markov chain associated with the one-dimensional Heisenberg (usually non-Markovian) process, obtained from this quantum Markov chain by restriction to a diagonal subalgebra, is such that all its states are recurrent. We were not able to obtain this result from the known recurrence criteria of classical probability.Supported by GNAFA-CNR, Bando n. 211.01.25.