解析Toeplitz算子的强不可约性

本文得到解析Toeplitz算子的强不可约性的一个充分条件，并且刻画了换位代数的k0-群．     

算子权移位的换位代数的交换性

令T是以{Wk}∞k=1B(Cn)为权序列的内射算子权移位.设T是强不可约的,而且sup1k<∞‖W-1k‖< ∞.用A′(T)表示T的换位代数,radA′(T)表示A′(T)的Jacobson根.本文刻划了radA′(T)并且证明了商代数A′(T)/radA′(T)是交换的.     

算子强不可约的充要条件

本文证明了Cowen-Douglas 算子是强不可约的充要条件,是它的换位代数模去其Jacobson 根同构于$H^{\infty}(D)$中的一个闭子代数,这里$D$表示开单位圆盘, $H^{\infty}(D)$表示$D$上的有界解析函数的全体.     

Wandering r-tuples for unitary systems

The properties of the set Wr(U) of all complete wandering r-tuples for a system U of unitary operators acting on a Hilbert space are investigated by parameterizing Wr(U) in terms of a fixed wandering r-tuple Ψ and the set of all unitary operators which locally commute with U at Ψ. The special case of greatest interest is the system 〈D,T〉 of dilation (by 2) and translation (by 1) unitary operators acting on L²(R), for which the complete wandering r-tuples are precisely the orthogonal multiwavelets with multiplicity r. We also give some examples for its application.     

Further results on several types of generalized inverses

Let R be an associative ring with unity 1 and let a,b,c∈R. In this paper, several characterizations for hybrid (b,c)-inverses of a are given. Also, the hybrid (b,c)-inverse of a is characterized by the group inverse of ab, under certain hypothesis. In particular, existence criteria for the the inverse along an element are obtained. Finally, we get the double commutant property and the reverse order law of annihilator (b,c)-inverses.     

加权Bergman空间上解析Toeplitz算子的换位及相似

本文在加权Bergman 空间A_α²(D)(α>-1) 上证明了由n-Blaschke 因子诱导的解析Toeplitz算子相似于n个Bergman 移位的直接和, 刻画了一类解析Toeplitz 算子的换位并研究了两个解析Toeplitz 算子的相似性.     

The commutant of analytic Toeplitz operators on Bergman space

In this paper, using the matrix skills and operator theory techniques we characterize the commutant of analytic Toeplitz operators on Bergman space. For f（z） = z^ng（z） （n ≥1）, g（z） = b0 ＋ b1z^p1 ＋b2z^p2 ＋.. , bk ≠ 0 （k = 0, 1, 2,...）, our main result is =A′（Mf） = A′（Mzn）∩A′（Mg） = A′（Mz^s）, where s = g.c.d.（n,p1,p2,...）. In the last section, we study the relation between strongly irreducible curve and the winding number W（f,f（α））, α ∈ D.     

On the classification and modular extendability of E0-semigroups on factors

In this paper we study modular extendability and equimodularity of endomorphisms and E₀-semigroups on factors, when these definitions are recast to the context of faithful normal semifinite weights and this dependency is analyzed. We show that modular extendability is a property that does not depend on the choice of weights, it is a cocycle conjugacy invariant and it is preserved under tensoring. Furthermore, we prove a necessary and sufficient condition for equimodularity of endomorphisms in the context of weights. This extends previously known results regarding the necessity of this condition in the case of states. The classification of E₀-semigroups on factors is considered: a modularly extendable E₀-semigroup is said to be of type EI, EII or EIII if its modular extension is of type I, II or III, respectively. We prove that all types exist on properly infinite factors. We show that q-CCR flows are not extendable, and we extend previous results by the first author regarding the non-extendability of CAR flow to a larger class of quasi-free states. We also compute the coupling index and the relative commutant index for the CAR flows and q-CCR flows. As an application, by considering repeated tensors of the CAR flows we show that there are infinitely many non cocycle conjugate non-extendable E₀-semigroups on the hyperfinite factors of types II₁ and III_λ, for $\text{◂+▸}\lambda \in (0,1)$.     

On a problem of Axler, Cuckovic and Rao

In this note we show that if two Toeplitz operators on a Bergman space of the (Levi) pseudoconvex domain commute and the symbol of one of them is analytic and non-constant, then the other one is also analytic. This gives an affirmative answer of a problem of S. Axler, Z. Cuckovic and N. V. Rao (1999).