共查询到20条相似文献,搜索用时 15 毫秒
1.
R. Słowik 《Acta Mathematica Hungarica》2016,148(2):386-404
We describe strong commutativity preservers on the algebra of infinite upper triangular matrices over a field F such that char\({(F) \neq 2}\). We show that every such map is some kind of a sum of a few sorts of maps. We also discuss the form of the maps that preserve commutativity in both directions. 相似文献
2.
3.
We study permanence properties of the classes of stable and so-called -stable -algebras, respectively. More precisely, we show that a (X)-algebra A is stable if all its fibres are, provided that the underlying compact metrizable space X has finite covering dimension or that the Cuntz semigroup of A is almost unperforated (a condition which is automatically satisfied for -algebras absorbing the Jiang–Su algebra tensorially). Furthermore, we prove that if is a K
1-injective strongly self-absorbing -algebra, then A absorbs tensorially if and only if all its fibres do, again provided that X is finite-dimensional. This latter statement generalizes results of Blanchard and Kirchberg. We also show that the condition
on the dimension of X cannot be dropped. Along the way, we obtain a useful characterization of when a -algebra with weakly unperforated Cuntz semigroup is stable, which allows us to show that stability passes to extensions of
-absorbing -algebras.
Research supported by: Deutsche Forschungsgemeinschaft (through the SFB 478), by the EU-Network Quantum Spaces - Noncommutative
Geometry (Contract No. HPRN-CT-2002-00280), and by the Center for Advanced Studies in Mathematics at Ben-Gurion University 相似文献
4.
We construct a hereditarily indecomposable Banach space with dual space isomorphic to ℓ 1. Every bounded linear operator on this space is expressible as λI + K, with λ a scalar and K compact. 相似文献
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6.
In this paper, we study properties of the topological space of composition operators acting on the space \({\mathcal{H}^{\infty}}\) of Dirichlet series. Especially, we show that there are two compact composition operators which are not in the same path component on \({\mathcal{H}^{\infty}}\). This is in sharp contrast with the classical case where all compact composition operators on \({H^{\infty}}\) of one variable or several variables lie in the same path component. 相似文献
7.
Ilie Burdujan 《Advances in Applied Clifford Algebras》2008,18(1):1-8
In this note, a group characterization for Clifford algebras of type is given. 相似文献
8.
Francisco Martin Masaaki Umehara Kotaro Yamada 《Calculus of Variations and Partial Differential Equations》2009,36(1):119-139
We construct a simply connected complete bounded mean curvature one surface in the hyperbolic 3-space ${\mathcal {H}^3}$ . Such a surface in ${\mathcal {H}^3}$ can be lifted as a complete bounded null curve in ${\rm {SL}(2,\mathbb {C})}$ . Using a transformation between null curves in ${\mathbb {C}^3}$ and null curves in ${\rm {SL}(2,\mathbb {C})}$ , we are able to produce the first examples of complete bounded null curves in ${\mathbb {C}^3}$ . As an application, we can show the existence of a complete bounded minimal surface in ${\mathbb {R}^3}$ whose conjugate minimal surface is also bounded. Moreover, we can show the existence of a complete bounded immersed complex submanifold in ${\mathbb {C}^2}$ . 相似文献
9.
Miroslav Bulí?ek Jens Frehse 《Calculus of Variations and Partial Differential Equations》2012,43(3-4):441-462
We consider weak solutions to nonlinear elliptic systems in a W 1,p -setting which arise as Euler equations to certain variational problems. The solutions are assumed to be stationary in the sense that the differential of the variational integral vanishes with respect to variations of the dependent and independent variables. We impose new structure conditions on the coefficients which yield everywhere ${\mathcal{C}^{\alpha}}$ -regularity and global ${\mathcal{C}^{\alpha}}$ -estimates for the solutions. These structure conditions cover variational integrals like ${\int F(\nabla u)\; dx}$ with potential ${F(\nabla u):=\tilde F (Q_1(\nabla u),\ldots, Q_N(\nabla u))}$ and positively definite quadratic forms in ${\nabla u}$ defined as ${Q_i(\nabla u)=\sum_{\alpha \beta} a_i^{\alpha \beta} \nabla u^\alpha \cdot \nabla u^\beta}$ . A simple example consists in ${\tilde F(\xi_1,\xi_2):= |\xi_1|^{\frac{p}{2}} + |\xi_2|^{\frac{p}{2}}}$ or ${\tilde F(\xi_1,\xi_2):= |\xi_1|^{\frac{p}{4}}|\xi_2|^{\frac{p}{4}}}$ . Since the Q i need not to be linearly dependent our result covers a class of nondiagonal, possibly nonmonotone elliptic systems. The proof uses a new weighted norm technique with singular weights in an L p -setting. 相似文献
10.
Jacques Wolfmann 《Designs, Codes and Cryptography》2000,20(1):73-88
Let R=GR(4,m) be the Galois ring of cardinality 4m and let T be the Teichmüller system of R. For every map λ of T into { -1,+1} and for every permutation Π of T, we define a map φ λ Π of Rinto { -1,+1} as follows: if x∈R and if x=a+2b is the 2-adic representation of x with x∈T and b∈T, then φ λ Π (x)=λ(a)+2Tr(Π(a)b), where Tr is the trace function of R . For i=1 or i=-1, define D i as the set of x in R such thatφ λ Π =i. We prove the following results: 1) D i is a Hadamard difference set of (R,+). 2) If φ is the Gray map of R into ${\mathbb{F}}_2^{2m}$ , then (D i) is a difference set of ${\mathbb{F}}_2^{2m}$ . 3) The set of D i and the set of φ(D i) obtained for all maps λ and Π, both are one-to-one image of the set of binary Maiorana-McFarland difference sets in a simple way. We also prove that special multiplicative subgroups of R are difference sets of kind D i in the additive group of R. Examples are given by means of morphisms and norm in R. 相似文献
11.
Dong Zhe 《Czechoslovak Mathematical Journal》2006,56(2):287-298
In this paper we investigate finite rank operators in the Jacobson radical
of Alg(
), where
are nests. Based on the concrete characterizations of rank one operators in Alg(
) and
, we obtain that each finite rank operator in
can be written as a finite sum of rank one operators in
and the weak closure of
equals Alg(
) if and only if at least one of
is continuous. 相似文献
12.
We show that every surface in the component \({\mathcal{H}^{\rm hyp}(4)}\) , that is the moduli space of pairs \({(M,\omega)}\) where M is a genus three hyperelliptic Riemann surface and \({\omega}\) is an Abelian differential having a single zero on M, is either a Veech surface or a generic surface, i.e. its \({{\rm GL}^{+}(2,\mathbb{R})}\) -orbit is either a closed or a dense subset of \({\mathcal{H}^{\rm hyp}(4)}\) . The proof develops new techniques applicable in general to the problem of classifying orbit closures, especially in low genus. Combined with work of Matheus and the second author, a corollary is that there are at most finitely many non-arithmetic Teichmüller curves (closed orbits of surfaces not covering the torus) in \({\mathcal{H}^{\rm hyp}(4)}\) . 相似文献
13.
George M. Bergman 《Algebra Universalis》2005,53(2-3):357-395
Properties of several sorts of lattices of convex subsets of
are examined. The lattice of convex sets containing the origin turns out, for n > 1, to satisfy a set of identities strictly between those of the lattice of all convex subsets of
and the lattice of all convex subsets of
The lattices of arbitrary, of open bounded, and of compact convex sets in
all satisfy the same identities, but the last of these is join-semidistributive, while for n > 1 the first two are not. The lattice of relatively convex subsets of a fixed set
satisfies some, but in general not all of the identities of the lattice of “genuine” convex subsets of
To the memory of Ivan RivalReceived April 22, 2003; accepted in final form February 16, 2005.This revised version was published online in August 2005 with a corrected cover date. 相似文献
14.
P. W. Ng 《Integral Equations and Operator Theory》2016,86(1):13-40
Let \({C^*_r(\mathbb{F}_{\infty})}\) be the reduced C*-algebra of the free group on infinitely many generators. Say that \({a, b \in C^*_r(\mathbb{F}_{\infty})_{SA}}\). Then \({a}\) is majorized by \({b}\) if and only if \({a \in \overline{Conv(U(b))}.}\) In particular, \({\tau(b)1 \in \overline{Conv(U(b))}.}\) Moreover, in the above results, we provide uniform bounds for the number of unitary conjugates needed for a given approximation. In the above, \({Conv(U(b))}\) is the convex hull of the unitary orbit of \({b}\) in \({C^*_r(\mathbb{F}_{\infty})}\). 相似文献
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16.
In this paper we discuss D’Angelo finite type pseudoconvex domains Ω in ${\mathbb C^3}$ . We are interested in complex curves tangent to higher order. Our main result is that there are only finitely many curves of maximal type. Maximal type has to be taken in a micro-local sense since the maximal type can be different in different directions. And of course to get finiteness we have to ignore higher order irrelevant terms which can be added without restriction. In the process of describing such a curve we find a singular change of coordinates which reduces the curve to a complex line. 相似文献
17.
In this paper, we initiate the study of contact and minimal hypersurfaces in nearly Kaehler manifold \({\mathbb {S}}^3\times {\mathbb {S}}^3\) with a conformal vector field. There are three almost contact metric structures on a hypersurface of \({\mathbb {S}}^3\times {\mathbb {S}}^3\), and we will give some important properties of them. Besides, we study the influence of the conformal vector field on the almost contact metric structures and use it to characterize the hypersurfaces in \({\mathbb {S}}^3\times {\mathbb {S}}^3\). 相似文献
18.
Jianfeng Huang Yulin Zhao 《NoDEA : Nonlinear Differential Equations and Applications》2013,20(6):1771-1794
In this paper we define an extended quasi-homogeneous polynomial system d x/dt = Q = Q 1 + Q 2 + ... + Q δ , where Q i are some 3-dimensional quasi-homogeneous vectors with weight α and degree i, i = 1, . . . ,δ. Firstly we investigate the limit set of trajectory of this system. Secondly let Q T be the projective vector field of Q. We show that if δ ≤ 3 and the number of closed orbits of Q T is known, then an upper bound for the number of isolated closed orbits of the system is obtained. Moreover this upper bound is sharp for δ = 3. As an application, we show that a 3-dimensional polynomial system of degree 3 (resp. 5) admits 26 (resp. 112) isolated closed orbits. Finally, we prove that a 3-dimensional Lotka-Volterra system has no isolated closed orbits in the first octant if it is extended quasi-homogeneous. 相似文献
19.
Zhaobo HUANG 《数学年刊B辑(英文版)》2010,31(4):491-496
The author constructs a sequence of cubes in the infinitely dimensional hyperbolic space H∞ which is equi-coarsely equivalent to Z2n. As a corollary, it is proved that the infinitely dimensional hyperbolic space H∞ does not have property A. 相似文献
20.
Yi Hu 《Compositio Mathematica》1999,118(2):159-187
In this paper, certain natural and elementary polygonal objects in Euclidean space, the stable polygons, are introduced, and the novel moduli spaces
of stable polygons are constructed as complex analytic spaces. Quite unexpectedly, these new moduli spaces are shown to be projective and isomorphic to the moduli space
of the Deligne–Mumford stable curves of genus 0. Further, built into the structures of stable polygons are some natural data giving rise to a family of (classes of) symplectic (Kähler) forms. This, via the link to
, brings up a new tool to study the Kähler topology of
. A wild but precise conjecture on the shape of the Kähler cone of
is given in the end. 相似文献