环面代数扩张的同态

本文研究了环面代数(即C(T2))扩张问同态的性质．设E1和E2为环面代数通过K的本质酉扩张,φ,ψ:E1→E2为单同态,若φ,ψ在半群V(E1)及商代数上导出的映射一致,则φ与ψ是近似酉等价的．这里K为可分的无限维复Hilbert空间上的紧算子全体构成的C*-代数,V(E1)为E1的矩阵代数中投影的Murray-von Neumann等价类构成的交换半群．     

保持算子乘积投影的线性映射

设B(H)是复Hilbert空间H上的有界线性算子全体且dim H≥2.本文证明了B(H)上的线性满射φ保持两个算子乘积非零投影性的充分必要条件是存在B(H)中的酉算子U以及复常数λ满足λ~2=1,使得φ(X)=λU~*XU,(?)X∈B(H).同时也得到了线性映射保持两个算子Jordan三乘积非零投影的充分必要条件.     

一类三角代数上的等距映射

本文研究了一类极大三角代数上满的线性等距映射。证明了这样的等距映射具有形式A→UAW或A→UJA*JW,这里U和W是适当的酉算子,J是某个固定的Hilbert空间上的对合。     

完全分配格上的φ－Pawlak代数

在完全分配格L的基础上,通过从分子到一般元素的映射φ,抽象地定义L上的两个一元算子,即下方φ-近似算子型,和上方φ-近似算子^——aprφ,可证明（L,∨,∧,^c,O,1,apr——φ,^——aprφ）在一定条件下是一个Pawlak代数,称为φ－Pawlak代数．并给出了下方φ－近似算子apr——φ,和上方φ－近似算子^——aprφ的一些代数性质．     

C~*标准代数中效应的序列同构

主要借助于C~*标准算子代数中的有限秩算子对一般的效应元进行刻画.证明了C~*标准算子代数A的效应代数E(A)上的每个序列自同构和自同构ψ都具有形式ψ(A)=UAU~*,其中A∈E(A),U为酉算子或反酉算子.     

多个算子情形的Kadison不等式

假设φ是一个从有单位元的C~*代数到Hilbert空间上全体有界线性算子构成的代数B(H)上的保单位的正线性映射,经典的Kadison不等式是指对每个自伴元素A有φ(A)~2≤φ(A~2),该文利用Furuta不等式把这一不等式推广至多个算子情形.     

保持算子乘积谱函数的映射

设A和B为无限维复Banach空间上的标准算子代数,记ΔR(·)为下列谱函数之一σR(·),σRl(·),σRr(·),σRl(·)∩σRr(·),(a)σR(·),ησR(·),σRp(·),σRc(·),σRap(·),σRs(·),σRap(·)∩σRs(·),σRp(·)∩σRc(·),σRp(·)∪σRc(·),其中R=A或B.证明了A和B之间的每个保持算子Jordan三乘积(算子乘积)之谱函数ΔR(·)的满射φ必有形式φ=επ,其中ε是1的立方根(1的平方根)而π或者是A和B之间的代数同构,或者是代数反同构.也获得不定度规空间上的标准算子代数之间保持算子斜乘积之谱函数的映射的完全刻画.     

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．     

Dirichlet空间上一类乘法算子的酉等价类

本文研究了Dirichlet空间D上由二阶Blaschke积φ定义的乘法算子M_φ的酉等价类.主要结果表明对于D的一个乘子ψ,乘法算子M_ψ酉等价于M_φ当且仅当存在常数θ,|θ|θ=1,使得ψ(z)=φ(θz).这一结果是完全不同于Hardy空间与Bergman空间上的相应结果.     

Nest代数的Jacobson根的μ-核值保持映射

设算子代数Ａ　Ｂ（Ｈ），μ（Ａ）表示Ａ中的部分等距算子全体，若ｐ是Ａ到Ｂ（Ｈ）的线性映射，且对任意的ＵＥｕ（Ａ），有叫Ｕ）（ｋｅｃＵ）Ｇｒ“ｈＣｒ，则称　是Ａ上的μ－核值保持映射。本文将证明：Ｎｅｓｔ代数的Ｊａｃｏｂｓｏｎ根上的范数拓扑连续的μ－核值保持映射是广义内导子。     

Linear maps on operator algebras that preserve elements annihilated by a polynomial

In this paper some purely algebraic results are given concerning linear maps on algebras which preserve elements annihilated by a polynomial of degree greater than 1 and with no repeated roots and applied to linear maps on operator algebras such as standard operator algebras, von Neumann algebras and Banach algebras. Several results are obtained that characterize such linear maps in terms of homomorphisms, anti-homomorphisms, or, at least, Jordan homomorphisms.

     

标准算子代数上完全保对合性的可加映射

刻画了无限维实或复Banach空间上的标准算子代数间完全保对合性的可加映射,证明了这样的映射是同构的常数倍或(复情形下)共轭同构的常数倍.     

Statistical Properties of Endomorphisms and Compact Group Extensions

The statistical properties of endomorphisms under the assumptionthat the associated Perron–Frobenius operator is quasicompactare considered. In particular, the central limit theorem, weakinvariance principle and law of the iterated logarithm for sufficientlyregular observations are examined. The approach clarifies therole of the usual assumptions of ergodicity, weak mixing, andexactness. Sufficient conditions are given for quasicompactness of thePerron–Frobenius operator to lift to the correspondingequivariant operator on a compact group extension of the base.This leads to statistical limit theorems for equivariant observationson compact group extensions. Examples considered include compact group extensions of piecewiseuniformly expanding maps (for example Lasota–Yorke maps),and subshifts of finite type, as well as systems that are nonuniformlyexpanding or nonuniformly hyperbolic.     

Applications of Wigner’s theorem to positive maps preserving norm of operator products

We apply Wigner’s theorem to positive maps on standard operator algebras that preserve norm of operator products or sum of singular values of operator products. It follows that such preservers are of the form ϕ(A) = U AU* with U either a unitary or antiunitary operator. Selected from Journal of Mathematical Study, 2004, 37(1): 11–16     

Phase space universality for multimodal maps

We study the dynamics of the renormalization operator for multimodal maps. In particular, we develop a combinatorial theory for certain kind of multimodal maps. We also prove that renormalizations of infinitely renormalizable multimodal maps with same bounded combinatorial type are exponentially close. Our results imply, for instance, the existence and uniqueness of periodic points for the renormalization operator with arbitrary combinatorial type.     

The q-Heun operator of big q-Jacobi type and the q-Heun algebra

The Ramanujan Journal - The q-Heun operator of the big q-Jacobi type on the exponential grid is defined. This operator is the most general second-order q-difference operator that maps polynomials...     

Block-matrix generalizations of infinite-dimensional schur products and schur multipliers

We consider an extention of the familiar Schur product to a bilinear product on the space of matrices whose entries are either bounded operators on a fixed Hilbert space or bounded "square" operator matrices. We show that this is a "natural" non-commutative extention of the Schur product, which retains many of its properties. The work is done mainly in infinite dimensions, where we concentrate on the maps induced on the space of bounded operator matrices via left or right "Schur block-multiplication" by a fixed "Schur block-multiplier". Our main goal is to study the distinctions between left and right multipliers, as well as the behaviour of ideals of operators under action of maps induced bu such.     

Common fixed-points for Banach operator pairs in best approximation

The notion of Banach operator pairs is introduced, as a new class of noncommuting maps. Some common fixed-point theorems for Banach operator pairs and the existence of the common fixed-points of best approximation are presented. These results are proved without the assumption of linearity or affinity for either f or g, which shows that the concept about Banach operator pairs is potentially useful in the study of common fixed-points.     

B(H)上保算子*乘积κ-幂零性的映射

将B(H)上保算子幂零性映射的研究由有限维推广到无限维,主要给出维数大于等于3的实或复的Hilbert空间算子代数上保算子*乘积k-幂零性映射的刻画.     

Quantum dynamical semigroups,symmetry groups,and locality

A survey of the recent work on the infinitesimal generators of one-parameter semigroups of positivity preserving maps on operator algebras, in the presence of compact symmetry groups or flows.