A SIMPLICIAL ALGORITHM FOR COMPUTING AN INTEGER ZERO POINT OF A MAPPING WITH THE DIRECTION PRESERVING PROPERTY

A mapping f:Z~n→R~n is said to possess the direction preserving property if fi(x)>0implies fi(y)≥0 for any integer points x and y with ‖x-y‖∞≤1.In this paper,a simplicial algorithm is developed for computing an integer zero point of a mappingwith the direction preserving property.We assume that there is an integer point x~0 withc≤x~0≤d satisfying that max_(1≤i≤n)(x_i-x_i~0)fi(x)>0 for any integer point x withf(x)≠0 on the boundary of H={x∈R~n|c-e≤x≤d e},where c and d are twofinite integer points with c≤d and e=(1,1,…1)~∈R~n.This assumption is impliedby one of two conditions for the existence of an integer zero point of a mapping with thepreserving property in van der Laan et al.(2004).Under this assumption, starting at x~0,the algorithm follows a finite simplicial path and terminates at an integer zero point ofthe mapping.This result has applications in general economic equilibrium models withindivisible commodities.     

On Universally Left-stability of ε-Isometry

LetX,Y be two real Banach spaces andε≥0.A map f:X→Y is said to be a standardε-isometry if|f(x)f(y)x y|≤εfor all x,y∈X and with f(0)=0.We say that a pair of Banach spaces(X,Y)is stable if there existsγ0 such that,for every suchεand every standardε-isometry f:X→Y,there is a bounded linear operator T:L(f)≡spanf(X)→X so that T f(x)x≤γεfor all x∈X.X(Y)is said to be universally left-stable if(X,Y)is always stable for every Y(X).In this paper,we show that if a dual Banach space X is universally left-stable,then it is isometric to a complemented w-closed subspace of∞(Γ)for some setΓ,hence,an injective space;and that a Banach space is universally left-stable if and only if it is a cardinality injective space;and universally left-stability spaces are invariant.     

第(16)类压缩映象的不动点定理

Let X be a complete metric space with distance function d, and T a mapp-ing from X into X. T is said to be a contractive mapping (16), if for any x, y∈ X, x ≠ y , it satisfies the following condition.     

Cauchy-Rassias Stability of Cauchy-Jensen Additive Mappings in Banach Spaces

Let X, Y be vector spaces. It is shown that if a mapping f ： X → Y satisfies f（（x＋y）/2＋z）＋f（（x-y）/2＋z=f（x）＋2f（z）,（0.1） f（（x＋y）/2＋z）-f（（x-y）/2＋z）f（y）,（0.2） or 2f（（x＋y）/2＋x）=f（x）＋f（y）＋2f（z）（0.3）for all x, y, z ∈ X, then the mapping f ： X →Y is Cauchy additive. Furthermore, we prove the Cauchy-Rassias stability of the functional equations （0.1）, （0.2） and （0.3） in Banach spaces. The results are applied to investigate isomorphisms between unital Banach algebras.     

Strong skew commutativity preserving maps on rings with involution

Let R be a unital *-ring with the unit I.Assume that R contains a symmetric idempotent P which satisfies ARP = 0 implies A = 0 and AR(I-P) = 0 implies A = 0.In this paper,it is shown that a surjective map Φ:R→R is strong skew commutativity preserving(that is,satisfiesΦ(A)Φ(B)-Φ(B)Φ(A)~w= AB-BA~w for all A,B∈R) if and only if there exist a map f:R→Z_s(R)and an element Z∈Z_s(R) with Z~2=I such that Φ(A)=ZA +f(A) for all A∈R,where Z_s(R) is the symmetric center of R.As applications,the strong skew commutativity preserving maps on unital prime *-rings and von Neumann algebras with no central summands of type I_1 are characterized.     

Quasi-Normal Structure and Fixed Point of Nonlinear Mappings

Let (X,|| ||) be a Banach space. For $\Omega \subset X^*$ and $x\in X$ we introduce the following notations (p\geq 1 and n\in N) $|X|_{\Omega _p(n)}=sup{(\sum\limits_{f\in F} |f(x)|^p)^{1/p}:F \subset \Omega,|F|\leq n$ $|X|_{\Omega _\infty}=sup{|f(x)|:f\in \Omega}$ A convex subset E of X is said to have guasi-normal structure whenever there exists a norm 1 | on A which satisfies the following conditions; (i) E has norinal structure relative to the norm ||| |||. (ii) There exist $\Omega \subset X^*$, p\geq 1 and \theta \in (0,1], such that $|x|_{\Omega _p(2) \leq |||x||| \leq ||x||}$ for x\in E and |||x|||<||x|| implies $2^1/p |x|_\Omega_\infty \geq \theta ||x||+(1-\theta)|||x|||$ or (ii)' There exist \Omega \subset X^*,p\geq 1 and \alpha \in [1,4^1/p) such that for all x\in E, |x|_\Omega_\rho(4)\leq |||x|||,||x||=max{|||x|||,\alpha|x|_\Omega_\infty} and for any countable subset w of \Omega $sup{\sum\limits _{\delt\in w |f(x)|^p:x\in E}<+\infty$ We notice that a set with normal steucture must have quasi-normal structure and there exist sets without normal structure which quasi-normal structure. The main result of the present paper is as follows. Theorem. Let (X, || ||) be a Banach space, E a weak compact convex nonempty subset of X with quasi-normal structure. Let T be a mapping of E in to itself. If there exists a sequence {x_n} in any T-invariant convex subset of E such that $lim_{n\rightarrow \infty} ||x_n-x_n+1||=lim_{n\rightarrow \infty}||x_n-Tx_n||=0$ and $lim_{n\rightarrow \infty} ||y-x_n||=\delta(\bar co{x_n}),for y\in \bar co({c_n})$ limll2/-*?ll=3(coK}), for y€co({xa}), then the mapping T has a fixed point in E, In particular, if the mapping T satisfies $||Tx-Ty||\leq max{||x-y||,1/2(||x-Ty||+||y-Tx||)},for x,y\in E$ then the mapping T has a fixed point in E.     

A relative local variational principle for topological pressure

We define the relative local topological pressure for any given factor map and open cover,and prove the relative local variational principle of this pressure.More precisely,for a given factor map π:(X,T)→(Y,S) between two topological dynamical systems,an open cover U of X,a continuous,real-valued function f on X and an S-invariant measure ν on Y,we show that the corresponding relative local pressure P(T,f,U,y) satisfies sup μ∈M(X,T){ hμ(T,U|Y)+∫X f(x)dμ(x) :πμ=ν}=∫Y P(T,f,U,y)dν(y),where M(X,T) denotes the family of all T-invariant measures on X.Moreover,the supremum can be attained by a T-invariant measure.     

CONSERVATIVE ESTIMATING FUNCTIONIN THE NONLINEAR REGRESSION MODEL WITHAGGREGATED DATA

1 IntroductionWe consider following nonlinear regression model:where y = (yi, y25..., yn)" is an n x 1 response vector with expectationwhere pi(0) = f(xi, 0), i = 1, 2,... 5 n; 0 = (91, 92,... I or)" is a p x I vector of unknown parameters, 0 E O C Re; fi is a q x 1 desigll variable, fi E X, X C Rq, i = 1, 2,... t n; f(., .) is a knownfunction, its field of definition is X x O; V(P(0)) is a positive definite matrix for all 0 E O.Let Y be the n-dimensional sample space. Suppose that on …     

Approximately Linear Mappings in Banach Modules over a C^＊-algebra

Let X and Y be vector spaces. The authors show that a mapping f ： X →Y satisfies the functional equation 2d f（∑^2d j=1（-1）^j＋1xj/2d）=∑^2dj=1（-1）^j＋1f（xj） with f（0） = 0 if and only if the mapping f ： X→ Y is Cauchy additive, and prove the stability of the functional equation （≠） in Banach modules over a unital C^＊-algebra, and in Poisson Banach modules over a unital Poisson C＊-algebra. Let A and B be unital C^＊-algebras, Poisson C^＊-algebras or Poisson JC^＊- algebras. As an application, the authors show that every almost homomorphism h ： A →B of A into is a homomorphism when h（（2d-1）^nuy） =- h（（2d-1）^nu）h（y） or h（（2d-1）^nuoy） = h（（2d-1）^nu）oh（y） for all unitaries u ∈A, all y ∈ A, n = 0, 1, 2,.... Moreover, the authors prove the stability of homomorphisms in C^＊-algebras, Poisson C^＊-algebras or Poisson JC^＊-algebras.     

Some Results Related to Metric Projection in Orlicz Sequence Spaces

Let X be a Banach space,and D a subset of X.A metric projection PD:X→ 2 Dis de-fined by PD(x) ={ y∈ D:‖ x-y‖ =d(x,D) } .D is a proximal (resp.Chebysev) setif PD contains at least(resp.exactly) one point.For a proximal set D,PD is callednorm-norm(norm-week) upper semi-continuous at x if for every normed(weak) openset W PD,there exists a normed neighborhood U of x such that PD(y) W for all y inU.It is proved in[1 ] that if X has C- (C- ) property PDis continuous for a Cheby-sev…     

改进的Tsirelson空间TM上的Wigner定理

设X和Y是赋范空间，如果映射f：X→Y满足{||f（x）+f（y）||，||f（x）-f（y）||}={||x+y||，||x-y||}（x，y∈X），则称f是一个相位等距算子.设g，f：X→Y是映射，若存在相位函数ε：X→{-1，1}，使得ε·f=g，则称g和f是相位等价的.本文将证明改进的Tsirelson空间T_M上的任意满相位等距算子均相位等价于一个线性等距算子.该结论同时也给出了改进的Tsirelson空间T_M上的Wigner型定理.     

Stability Characterizations of ε-isometries on Certain Banach Spaces

Suppose that X, Y are two real Banach Spaces. We know that for a standard ε-isometry f : X → Y, the weak stability formula holds and by applying the formula we can induce a closed subspace N of *. In this paper, by using again the weak stability formula, we further show a sufficient and necessary condition for a standard ε-isometry to be stable in assuming that N is w*-closed in Y*.Making use of this result, we improve several known results including Figiel's theorem in reflexive spaces.We also prove that if, in addition, the space Y is quasi-reflexive and hereditarily indecomposable, then L(f)≡span[f(X)] contains a complemented linear isometric copy of X; Moreover, if X =Y, then for every e-isometry f: X → X, there exists a surjective linear isometry S:X → X such that f-S is uniformly bounded by 2ε on X.     

单位球面上的等距算子的延拓

本文考虑一般的Banach空间上的等距延拓问题,利用赋范集的概念给出了一些充分条件,使得单位球面间的满等距算子可以延拓为全空间上的线性等距算子。     

On square roots of isometries

Abstract

In various normed spaces we answer the question of when a given isometry is a square of some isometry. In particular, we consider (real and complex) matrix spaces equipped with unitarily invariant norms and unitary congruence invariant norms, as well as some infinite dimensional spaces illustrating the difference between finite and infinite dimensions.     

A Mazur–Ulam theorem in non-Archimedean normed spaces

The classical Mazur–Ulam theorem which states that every surjective isometry between real normed spaces is affine is not valid for non-Archimedean normed spaces. In this paper, we establish a Mazur–Ulam theorem in the non-Archimedean strictly convex normed spaces.     

Malliavin calculus and decoupling inequalities in Banach spaces

We develop a theory of Malliavin calculus for Banach space-valued random variables. Using radonifying operators instead of symmetric tensor products we extend the Wiener-Itô isometry to Banach spaces. In the white noise case we obtain two sided Lp-estimates for multiple stochastic integrals in arbitrary Banach spaces. It is shown that the Malliavin derivative is bounded on vector-valued Wiener-Itô chaoses. Our main tools are decoupling inequalities for vector-valued random variables. In the opposite direction we use Meyer's inequalities to give a new proof of a decoupling result for Gaussian chaoses in UMD Banach spaces.     

The isometrical extensions of 1-Lipschitz mappings on Gteaux differentiability spaces

Let X and Y be real Banach spaces.Suppose that the subset sm[S1(X)] of the smooth points of the unit sphere [S1(X)] is dense in S1(X).If T0 is a surjective 1-Lipschitz mapping between two unit spheres,then,under some condition,T0 can be extended to a linear isometry on the whole space.     

Isometry groups of non standard metric products

We consider isometry groups of a fairly general class of non standard products of metric spaces. We present sufficient conditions under which the isometry group of a non standard product of metric spaces splits as a permutation group into direct or wreath product of isometry groups of some metric spaces.     

The space of left-invariant metrics on a Lie group up to isometry and scaling

We study the spaces of left-invariant Riemannian metrics on a Lie group up to isometry, and up to isometry and scaling. In this paper, we see that such spaces can be identified with the orbit spaces of certain isometric actions on noncompact symmetric spaces. We also study some Lie groups whose spaces of left-invariant metrics up to isometry and scaling are small.