Inverse Systems and I-Favorable Spaces
A compact space X is I-favorable if, and only if X can be representing as a limit of $σ$-complete inverse system of compact metrizable spaces with skeletal bonding maps.
math.GN↗
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Rips complexes and covers in the uniform category
James \cite{Jam} introduced uniform covering maps as an analog of covering maps in the topological category. Subsequently Berestovskii and Plaut \cite{BP3} introduced a theory of covers for uniform spaces generalizing their results for topological groups \cite{BP1}-\cite{BP2}. Their main concepts are discrete actions and pro-discrete actions, respectively. In case of pro-discrete actions Berestovskii and Plaut provided an analog of the universal covering space and their theory works well for the so-called coverable spaces. As will be seen in Section \ref{SECTION-Comparison}, \cite{BP3} generalizes only regular covering maps in topology and pro-discrete actions may not be preserved by compositions. In this paper we redefine the uniform covering maps and we generalize pro-discrete actions using Rips complexes and the chain lifting property. We expand the concept of generalized paths of Krasinkiewicz and Minc \cite{KraMin}.
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Zero-Bidimension and Various Classes of Bitopological Spaces
The sum theorem and its corollaries are proved for a countable family of zero-dimensional (in the sense of small and large inductive bidimensions) p-closed sets, using a new notion of relative normality whose topological correspondent is also new. The notion of almost $n$-dimensionality is considered from the bitopological point of view. Bitopological spaces in which every subset is i-open in its $j$-closure (i.e.,(i,j)-submaximal spaces) are introduced and their properties are studied. Based on the investigations begun in [5] and [14], sufficient conditions are found for bitopological spaces to be(1,2)-Baire in the class of p-normal spaces. Furthermore, (i,j)-I-spaces are introduced and both the relations between(i,j)-submaximal, (i,j)-nodec and (i,j)-I-spaces, and their properties are studied when two topologies on a set are either independent of each other or interconnected by the inclusion, S-, C- and N-relations or by their combinations. The final part of the paper deals with the questions of preservation of $(i,j)$-submaximal and $(2,1)\dd I$-spaces to an image, of $D$-spaces to an image and an inverse image for both the topological and the bitopological cases. Two theorems are formulated containing, on the one hand, topological conditions and, on the other hand, bitopological ones, under which a topological space is a $D$-space.
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On the Theory of Relative Bitopological and Topological Properties
In the first part of the work (Sections 2-6) a special attention is given to relative separation axioms and relative connectedness, in particular, many relative versions of p-T_0, p-T_1, p-T_2, (i,j)- and p-regularities, (i,j)- and p-complete regularities, p-real normality and p-normality are discussed. Moreover, relative properties of (i,j)- and p-compactness types, including relative versions of (i,j)- and p-paracompactness, (i,j)- and p-Lindeofness, (i,j)- and p-pseudocompactness are also introduced and investigated. The second part (Sections 7-12) is devoted, on the one hand, to relative bitopological inductive and covering dimension functions and, on the other hand, to relative versions of Baire spaces for both the topological and the bitopological case. At the end, note that relative (bi)topological properties play a special role not only in the development of respective theories, but also in the strengthening of the previously known results.
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A dichotomy characterizing analytic digraphs of uncountable Borel chromatic number in any dimension
We study the extension of the Kechris-Solecki-Todorcevic dichotomy on analytic graphs to dimensions higher than 2. We prove that the extension is possible in any dimension, finite or infinite. The original proof works in the case of the finite dimension. We first prove that the natural extension does not work in the case of the infinite dimension, for the notion of continuous homomorphism used in the original theorem. Then we solve the problem in the case of the infinite dimension. Finally, we prove that the natural extension works in the case of the infinite dimension, but for the notion of Baire-measurable homomorphism.
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Representation of finite connective spaces
After recalling the definition of connectivity spaces and some of their main properties, a way is proposed to represent finite connectivity spaces by directed simple graphs. Then a connectivity structure is associated to each tame link. It is showed that all spaces of a certain class (the iterated Brunnian ones) admit representations by links. Finally, I conjecture that every finite connectivity space is representable by a link. ----- Apres un rappel de la definition des espaces connectifs et de certaines de leurs principales proprietes, nous proposons une maniere de representer les espaces connectifs finis par des graphes simples orientes, puis nous associons a tout entrelacs une structure connective. Nous montrons que tout espace d'une certaine classe (les espaces brunniens iteres) admet une representation par entrelacs, et nous conjecturons finalement que tout espace connectif fini est representable par entrelacs.
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Advanced topology on the multiscale sequence spaces S^ν
We pursue the study of the multiscale spaces $S^ν$ introduced by Jaffard in the context of multifractal analysis. We give the necessary and sufficient condition for $S^ν$ to be locally p-convex, and exhibit a sequence of $p$-norms that defines its natural topology. The strong topological dual of $S^ν$ is identified to another sequence space depending on $ν$, endowed with an inductive limit topology. As a particular case, we describe the dual of a countable intersection of Besov spaces.
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Valdivia compact groups are products
It is shown that every Valdivia compact group is homeomorphic to a product of metrizable compacta.
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An equivalent condition for a uniform space to be coverable
We prove that an equivalent condition for a uniform space to be coverable is that the images of the natural projections in the fundamental inverse system are uniformly open in a certain sense. As corollaries we (1) obtain a concrete way to find covering entourage, (2) correct an error in [3] and (3) show that coverable is equivalent to chain connected and uniformly joinable in the sense of arXiv:0706.3937.
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Covering R-trees
We show that every inner metric space X is the metric quotient of a complete R-tree via a free isometric action, which we call the covering R-tree of X. The quotient mapping is a weak submetry (hence, open) and light. In the case of compact 1-dimensional geodesic space X, the free isometric action is via a subgroup of the fundamental group of X. In particular, the Sierpin'ski gasket and carpet, and the Menger sponge all have the same covering R-tree, which is complete and has at each point valency equal to the continuum. This latter R-tree is of particular interest because it is "universal" in at least two senses: First, every R-tree of valency at most the continuum can be isometrically embedded in it. Second, every Peano continuum is the image of it via an open light mapping. We provide a sketch of our previous construction of the uniform universal cover in the special case of inner metric spaces, the properties of which are used in the proof.
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A construction of noncontractible simply connected cell-like two dimensional Peano continua
Using the topologist sine curve we present a new functorial construction of cone-like spaces, starting in the category of all path-connected topological spaces with a base point and continuous maps, and ending in the subcategory of all simply connected spaces. If one starts by a noncontractible n-dimensional Peano continuum for any n>0, then our construction yields a simply connected noncontractible (n + 1)-dimensional cell-like Peano continuum. In particular, starting with the circle $\mathbb{S}^1$, one gets a noncontractible simply connected cell-like 2-dimensional Peano continuum.
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Large inductive dimension of the Smirnov remainder
The purpose of this paper is to investigate the large inductive dimension of the remainder of the Smirnov compactification of the n-dimensional Euclidean space with the usual metric, and give an application of it.
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A Short Study of Alexandroff Spaces
In this paper, we discuss the basic properties of Alexandroff spaces. Several examples of Alexandroff spaces are given. We show how to construct new Alexandroff spaces from given ones. Finally, two invariants for compact Alexandroff spaces are defined and calculated for the given examples.
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The uniform order convergence structure on ML(X)
The aim of this paper is to set up appropriate uniform convergence spaces in which to reformulate and enrich the Order Completion Method for nonlinear PDEs. In this regard, we consider an appropriate space ML(X) of normal lower semi-continuous functions. The space ML(X)= appears in the ring theory of C(X), and its various extensions, as well as in the theory of nonlinear PDEs. We define a uniform convergence structure on ML(X) such that the induced convergence structure is the order convergence structure. The uniform convergence space completion of ML(X) is constructed as the set of normal lower semi-continuous functions. It is then shown how these ideas may be applied to solve nonlinear PDEs. In particular, we construct generalized solutions to the Navier-Stokes equations in three spatial dimensions, subject to an initial condition.
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On topological spaces possessing uniformly distributed sequences
Two classes of topological spaces are introduced on which every probability Radon measure possesses a uniformly distributed sequence or a uniformly tight uniformly distributed sequence. It is shown that these classes are stable under multiplication by completely regular Souslin spaces
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Continuous functions taking every value a given number of times
We give necessary and sufficient conditions on a function $f:[0,1]\to {0,1,2,...,ω,\continuum}$ under which there exists a continuous function $F:[0,1]\to [0,1]$ such that for every $y\in[0,1]$ we have $|F^{-1}(y)|=f(y)$.
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Homotopy characterization of ANR mapping spaces
Let Y be an absolute neighborhood retract (ANR) for the class of metric spaces and let X be a Hausdorff space. Let map(X,Y) denote the space of continuous maps from X to Y with the compact open topology. It is shown that if X is a CW complex then map(X,Y) is an ANR for the class of metric spaces if and only if map(X,Y) is metrizable and has the homotopy type of a CW complex. The same holds also when X is a compactly generated hemicompact space (metrizability assumption is void in this case).
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Constructive decomposition of a function of two variables as a sum of functions of one variable
Given a compact set $K$ in the plane, which does not contain any triple of points forming a vertical and a horizontal segment, and a map $f\in C(K)$, we give a construction of functions $g,h\in C(\mathbb R)$ such that $f(x,y)=g(x)+h(y)$ for all $(x,y)\in K$. This provides a constructive proof of a part of Sternfeld's theorem on basic embeddings in the plane. In our proof the set $K$ is approximated by a finite set of points.
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