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1.
Věra Trnková 《Applied Categorical Structures》2004,12(4):379-396
Dualizing the statement about a number of components of a topological space X, we say that, for a natural number n, the space X has at most n cocomponents if every continuous map f:X
n+1X factorizes through X
n
, i.e., f depends on at most n coordinates. We construct metrizable spaces X
1,X
2,X
3 such that(1) X
1 does not have finitely many cocomponents but every continuous map X
1
X
1 depends only on finitely many coordinates;(2) X
2=A×B for rigid spaces A,B and there is a continuous map X
2
X
2 depending on all coordinates;(3) X
3(n) has precisely n cocomponents but it cannot be expressed as A×B with |A|>1 and |B|>1. 相似文献
2.
For every natural number n > 1, we construct a topological space X such that the clone segments of its Tychonoff modification T M X verify Clo
k
(X) = Clo
k
(T M X) if k < n and Clo
n
(X) is not isomorphic to Clo
n
(T M X). 相似文献
3.
Behnam Khosravi 《代数通讯》2018,46(7):3006-3013
For a finite monoid S, let ν(S) (νd(S)) denote the least number n such that there exists a graph (directed graph) Γ of order n with End(Γ)?S. Also let rank(S) be the smallest number of elements required to generate S. In this paper, we use Cayley digraphs of monoids, to connect lower bounds of ν(S) (νd(S)) to the lower bounds of rank(S). On the other hand, we connect upper bounds of rank(S) to upper bounds of ν(S) (νd(S)). 相似文献
4.
Let I=[0,1] and let P be a partition of I into a finite number of intervals. Let τ1, τ2; I→I be two piecewise expanding maps on P . Let G⊂I×I be the region between the boundaries of the graphs of τ1 and τ2. Any map τ:I→I that takes values in G is called a selection of the multivalued map defined by G . There are many results devoted to the study of the existence of selections with specified topological properties. However, there are no results concerning the existence of selection with measure-theoretic properties. In this paper we prove the existence of selections which have absolutely continuous invariant measures (acim). By our assumptions we know that τ1 and τ2 possess acims preserving the distribution functions F(1) and F(2). The main result shows that for any convex combination F of F(1) and F(2) we can find a map η with values between the graphs of τ1 and τ2 (that is, a selection) such that F is the η-invariant distribution function. Examples are presented. We also study the relationship of the dynamics of our multivalued maps to random maps. 相似文献
5.
We prove that an order unit can be adjoined to every L
∞-matricially Riesz normed space. We introduce a notion of strong subspaces. The matrix order unit space obtained by adjoining an order unit to an L
∞-matrically Riesz normed space is unique in the sense that the former is a strong L
∞-matricially Riesz normed ideal of the later with codimension one. As an application of this result we extend Arveson’s extension
theorem to L
∞-matircially Riesz normed spaces. As another application of the above adjoining we generalize Wittstock’s decomposition of
completely bounded maps into completely positive maps on C
*-algebras to L
∞-matricially Riesz normed spaces. We obtain sharper results in the case of approximate matrix order unit spaces.
Mathematics Subject Classification (2000). Primary 46L07 相似文献
6.
J.W. Snow 《Algebra Universalis》1999,42(4):299-309
We show that every sentence preserved by products in a purely relational first order language corresponds to a Maltsev condition
on subalgebras of direct powers. Moreover, we establish that this correspondence captures all strong Maltsev conditions whose
defining equations do not involve compositions. We then demonstrate how a broader version of the correspondence is sufficient
to capture all Maltsev conditions when we restrict our attention to locally finite varieties.
Received November 6, 1998; accepted in final form July 8, 1999. 相似文献
7.
S. I. El‐Zanati G. F. Seelinger P. A. Sissokho L. E. Spence C. Vanden Eynden 《组合设计杂志》2008,16(4):329-341
Let Vn(q) denote a vector space of dimension n over the field with q elements. A set of subspaces of Vn(q) is a partition of Vn(q) if every nonzero element of Vn(q) is contained in exactly one element of . Suppose there exists a partition of Vn(q) into xi subspaces of dimension ni, 1 ≤ i ≤ k. Then x1, …, xk satisfy the Diophantine equation . However, not every solution of the Diophantine equation corresponds to a partition of Vn(q). In this article, we show that there exists a partition of Vn(2) into x subspaces of dimension 3 and y subspaces of dimension 2 if and only if 7x + 3y = 2n ? 1 and y ≠ 1. In doing so, we introduce techniques useful in constructing further partitions. We also show that partitions of Vn(q) induce uniformly resolvable designs on qn points. © 2007 Wiley Periodicals, Inc. J Combin Designs 16: 329–341, 2008 相似文献
8.
Fazli Kh 《Statistical Inference for Stochastic Processes》2007,10(2):181-208
We observe a realization X
(n) of a Poisson process on the set
with intensity function
depending on the unknown real parameter
. Based on X
(n) we test simple null hypothesis
against one sided alternative
for given
. We improve the level of the well-known locally asymptotically uniformly most powerful (LAUMP) test by using the Edgeworth
type expansion for stochastic integral. We show that the improved test is second-order efficient under certain regularity
conditions.
相似文献
9.
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. 相似文献
10.
Nicolas Bouffard 《Nonlinear Analysis: Theory, Methods & Applications》2011,74(17):5815-5832
A semi-topological semigroup is strongly left amenable if there is a compact left ideal group in the spectrum of its LUC-compactification. In this paper, we want to study those objects, and study some fixed point property related to non-expansive mapping and other similar kind of mapping. 相似文献
11.
借鉴Orlicz-Sobolev空间中的受控最佳逼近算子问题的研究结果,抓住Musielak-Orlicz-Sobolev空间的构成特点,利用△_2条件及其否定,给出了MusielakOrlicz-Sobolev空间具有序连续性的充要条件,同时研究了该空间中最佳逼近算子的连续性. 相似文献
12.
Mark V. Lawson 《Semigroup Forum》2008,76(3):489-517
We describe a correspondence between a class of left cancellative monoids and self-similar group actions in the sense of Nekrashevych
et al. This correspondence originated in Perrot’s 1972 thesis, and developed the ideas to be found in Rees’ 1948 paper. 相似文献
13.
Pawe? Góra 《Journal of Mathematical Analysis and Applications》2006,317(1):257-270
We consider a random map T=T(Γ,ω), where Γ=(τ1,τ2,…,τK) is a collection of maps of an interval and ω=(p1,p2,…,pK) is a collection of the corresponding position dependent probabilities, that is, pk(x)?0 for k=1,2,…,K and . At each step, the random map T moves the point x to τk(x) with probability pk(x). For a fixed collection of maps Γ, T can have many different invariant probability density functions, depending on the choice of the (weighting) probabilities ω. Most of the results in this paper concern random maps where Γ is a family of piecewise linear semi-Markov maps. We investigate properties of the set of invariant probability density functions of T that are attainable by allowing the probabilities in ω to vary in a certain class of functions. We prove that the set of all attainable densities can be determined algorithmically. We also study the duality between random maps generated by transformations and random maps constructed from a collection of their inverse branches. Such representation may be of greater interest in view of new methods of computing entropy [W. S?omczyński, J. Kwapień, K. ?yczkowski, Entropy computing via integration over fractal measures, Chaos 10 (2000) 180-188]. 相似文献
14.
15.
J. K. Truss 《Order》2001,18(4):359-379
A classification was given by Creed, Truss, and Warren of all the countable k-CS-transitive cycle-free partial orders for k3. Here the elementary theories of these structures and their automorphism groups are examined, and it is shown that in many cases we can distinguish the structures or their groups by means of their first- or second-order properties. The small index property is established for weakly 2-transitive trees, and for several classes of cycle-free partial orders. 相似文献
16.
Existence and nonexistence of hypercyclic semigroups 总被引:1,自引:0,他引:1
L. Bernal-Gonzá lez K.-G. Grosse-Erdmann 《Proceedings of the American Mathematical Society》2007,135(3):755-766
In these notes we provide a new proof of the existence of a hypercyclic uniformly continuous semigroup of operators on any separable infinite-dimensional Banach space that is very different from--and considerably shorter than--the one recently given by Bermúdez, Bonilla and Martinón. We also show the existence of a strongly dense family of topologically mixing operators on every separable infinite-dimensional Fréchet space. This complements recent results due to Bès and Chan. Moreover, we discuss the Hypercyclicity Criterion for semigroups and we give an example of a separable infinite-dimensional locally convex space which supports no supercyclic strongly continuous semigroup of operators.
17.
某些Banach空间的有限阶光滑点和强光滑点(英) 总被引:2,自引:0,他引:2
本文给出l∞(X)以及L(l1(X),Y),L(X,l∞(Y))和L(X,c0(Y))的单位球的有限阶光滑点和强光滑点的充要条件,这里X和Y都是任意的Banach空间.特别地,本文给出这些空间的单位球的光滑点和强光滑点的充要条件. 相似文献
18.
19.
Jakub Gajarský Petr Hliněný Tomáš Kaiser Daniel Král’ Martin Kupec Jan Obdržálek Sebastian Ordyniak Vojtěch Tůma 《Random Structures and Algorithms》2017,50(4):612-635
Ne?et?il and Ossona de Mendez introduced the notion of first order convergence as an attempt to unify the notions of convergence for sparse and dense graphs. It is known that there exist first order convergent sequences of graphs with no limit modeling (an analytic representation of the limit). On the positive side, every first order convergent sequence of trees or graphs with no long path (graphs with bounded tree‐depth) has a limit modeling. We strengthen these results by showing that every first order convergent sequence of plane trees (trees with embeddings in the plane) and every first order convergent sequence of graphs with bounded path‐width has a limit modeling. © 2016 Wiley Periodicals, Inc. Random Struct. Alg., 50, 612–635, 2017 相似文献
20.
详细地研究了有限域 Fq上的矩阵的阶的问题 ,得到了相当理想的结果 .并给出一类矩阵方幂的极小多项式的求法 相似文献