Additive Maps Preserving Nilpotent Operators or Spectral Radius

Let X be a （real or complex） Banach space with dimension greater than 2 and let B0（X） be the subspace of B（X） spanned by all nilpotent operators on X. We get a complete classification of surjective additive maps Ф on B0（X） which preserve nilpotent operators in both directions. In particular, if X is infinite-dimensional, we prove that Ф has the form either Ф（T） = cATA^-1 or Ф（T） = cAT＇A^-1, where A is an invertible bounded linear or conjugate linear operator, c is a scalar, T＇ denotes the adjoint of T. As an application of these results, we show that every additive surjective map on B（X） preserving spectral radius has a similar form to the above with ｜c｜ = 1.     

Additive Maps Preserving Similarity of Operators on Banach Spaces

Let X be an infinite-dimensional complex Banach space and denote by B（X） the algebra of all bounded linear operators acting on X. It is shown that a surjective additive map Φ from B（X） onto itself preserves similarity in both directions if and only if there exist a scalar c, a bounded invertible linear or conjugate linear operator A and a similarity invariant additive functional ψ on B（X） such that either Φ（T） = cATA^-1 ＋ ψ（T）I for all T, or Φ（T） = cAT＊A^-1 ＋ ψ（T）I for all T. In the case where X has infinite multiplicity, in particular, when X is an infinite-dimensional Hilbert space, the above similarity invariant additive functional ψ is always zero.     

套代数上保秩一幂零性的可加映射

${\cal N}$和${\cal M}$分别是实或复Banach空间$X$ ($\dim X >5$)和$Y$中的两个套且Alg${\cal N}$和Alg${\cal M}$分别是与套${\cal N}$和${\cal M}$相关的套代数.符号Alg加映射;秩一幂零算子;套代数Additive map,Rank one nilpotent operator,Nest algebra国家自然科学基金;清华大学校科研和教改项目;教育部高等学校博士点教育基金;国家自然科学基金;山西省自然科学基金2005-02-082007年4月25日${\cal N}$和${\cal M}$分别是实或复Banach空间$X$ ($\dim X >5$)和$Y$中的两个套且Alg${\cal N}$和Alg${\cal M}$分别是与套${\cal N}$和${\cal M}$相关的套代数.符号Alg加映射;秩一幂零算子;套代数Additive map,Rank one nilpotent operator,Nest algebra国家自然科学基金;清华大学校科研和教改项目;教育部高等学校博士点教育基金;国家自然科学基金;山西省自然科学基金2005-02-082007年4月25日令N和M分别是实或复Banach空间X(dim X>5)和Y中的两个套且AlgN和AlgM分别是与套N和M相关的套代数．符号AlgFN表示AlgN中所有有限秩算子全体．设Φ:AlgFN→AlgFM是可加映射,且值域包含AlgFM中的所有秩一幂零元．如果Φ-双边保秩一幂零性,作者证明了存在一个域自同构τ及τ-线性算子A和C使得要么对所有的秩一幂零元x(?)f∈AlgFN,Φ(x(?)f)=Ax(?)Cf,要么对所有的秩一幂零元x(?)f∈AlgFN,Φ(x(?)f)=Af(?)Cx．特别地,当X和Y是Hilbert空间且Φ是连续映射时,作者得到这类可加映射Φ的完全刻画．     

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.     

保持算子截断的可加映射

Let H be a complex Hilbert space and B(H)the algebra of all bounded linear operators on H.An operator A is called the truncation of B in B(H)if A=P_ABP_A^*,where PA and P_A^*denote projections onto the closures of R(A)and R(A^*),respectively.In this paper,we determine the structures of all additive surjective maps on B(H)preserving the truncation of operators in both directions.     

自伴标准算子代数上强保持k-斜交换性映射的刻画

令H是维数大于2的复Hilbert空间,A是H上自伴标准算子代数.对于给定的正整数k≥1,H上算子A与B的k-斜交换子递推地定义为_*[A,B]_k=_*[A,_*[A,B]_k-1],其中_*[A,B]₀=B,_*[A,B]₁=AB-BA^*.设k≥4,φ是A上的值域包含所有一秩投影的映射.本文证明了φ满足_*[φ（A）,φ（B）]_k=_*[A,B]_k对任意A,B∈A都成立的充分必要条件是φ（A）=A对任意A∈A都成立,或φ（A）=-A对任意A∈A都成立.当k是偶数时后一情形不出现.     

关于可加保幂零映射的一点注记

给出Mn(F)(n≥2，F=R或C)上所有保幂零可加满射的刻画．作为应用，得到Mn(C)上保相似性可加满射，保谱等性可加满射以及保特征值相等可加满射的刻画．     

辛代数的极大幂零子代数的保李括积零的线性映射

Let F be a field with char F = 2, l a maximal nilpotent subalgebra of the symplectic algebra sp（2m,F）. In this paper, we characterize linear maps of l which preserve zero Lie brackets in both directions. It is shown that for m ≥ 4, a map φ of l preserves zero Lie brackets in both directions if and only if φ = ψcσT0λαφdηf, where ψc,σT0,λα,φd,ηf are the standard maps preserving zero Lie brackets in both directions.     

域上矩阵群逆的加法保持映射

在本文中,我们刻画了保持域上矩阵群逆的加法映射的形式.     

Additive Mappings Preserving Rank-one Idempotents

A complete characterization of additive mappings φ ： B（X）→B（Y）, which map rank-one idempotents to themselves or to zero, is given.     

On additive maps preserving certain semi-Fredholm subsets

Let X and Y be two infinite dimensional real or complex Banach spaces, and let φ: ?(X)?→??(Y) be an additive surjective mapping that preserves semi-Fredholm operators in both directions. In the complex Hilbert space context, Mbekhta and ?emrl [M. Mbekhta and P. ?emrl, Linear maps preserving semi-Fredholm operators and generalized invertibility, Linear Multilinear Algebra 57 (2009), pp. 55–64] determined the structure of the induced map on the Calkin algebra. In this article, we show the following: given an integer n?≥?1, if φ preserves in both directions ? _n (X) (resp., 𝒬 _n (X)), the set of semi-Fredholm operators on X of non-positive (resp., non-negative) index, having dimension of the kernel (resp., codimension of the range) less than n, then φ(T)?=?UTV for all T or φ(T)?=?UT*V for all T, where U and V are two bijective bounded linear, or conjugate linear, mappings between suitable spaces.     

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.     

次范整线性空间上的可加奇性算子

研究次范整线性空间上的可加奇性算子理论.引进可加奇性算子的三种不同的次范数和拟次范数,利用它们刻画可加奇性算子的三种有界性:有界、局部有界和球有界,深入讨论这三种有界性之间的关系,以及它们与连续性的关系.同时,还进一步研究次范整线性空间上连续可加奇性算子族的共鸣定理.     

Maps Preserving Zeros of xy*

For a prime ring A with involution, we explore the characterization of additive bijective maps φ: A → A such that φ(x)φ(y)* = 0 whenever xy* = 0. In particular, we show that if A is prime, unital, and generated by nontrivial idempotents, then there is a *-monomorphism g of A into Q, and an element r ∈ A such that φ(x) = rg(x) for all x ∈ A.     

Linear Maps Preserving Invertibility or Related Spectral Properties

We survey some recent results on linear maps on operator algebras that preserve invertibility. We also consider related problems such as the problem of the characterization of linear maps preserving spectrum, various parts of spectrum, spectral radius, quasinilpotents, etc. We present some results on elementary operators and additive operators preserving invertibility or related properties. In particular, we give a negative answer to a problem posed by Gao and Hou on characterizing spectrumpreserving elementary operators. Several open problems are also mentioned.     

Additive Maps Preserving the Star Partial Order on B(H)

Let B(H) be the C*-algebra of all bounded linear operators on a complex Hilbert space H. It is proved that an additive surjective map φ on B(H) preserving the star partial order in both directions if and only if one of the following assertions holds.(1) There exist a nonzero complex number α and two unitary operators U and V on H such that φ(X) = αUXV or φ(X) = αUX*V for all X ∈ B(H).(2)There exist a nonzero α and two anti-unitary operators U and V on H such thatφ(X) = αUXV or φ(X) = αUX*V for all X ∈ B(H).     

保不定半正交性的可加映射

设Hi是实或复数域上无限维完备的不定度规空间,Ai是B(Hi)中由单位元I和一个理想生成的子代数,其中B(Hi)表示Hi上所有有界线性算子构成的代数,i=1,2.本文刻画了从A1到A2上双边保不定半正交性的可加满射Ф,即对任意T,S∈A1,T S=0(=)Ф(T) Ф(S)=0.主要结果表明,这样的Ф具有形式Ф(T)=UTV对任意的T∈A1成立,这里U,V是有界线性或共轭线性可逆算子且U U=cI,c是非零实数.     

Additive Maps Preserving Local Spectrum

Let X be a complex Banach space, and let be the space of bounded operators on X. Given and x ∈ X, denote by σ_T (x) the local spectrum of T at x. We prove that if is an additive map such that