Module-valued functors preserving the covering dimension

Jan Spěvák

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Displaying similar documents to “Module-valued functors preserving the covering dimension”

A study of universal elements in classes of bases of topological spaces

Dimitris N. Georgiou, Athanasios C. Megaritis, Inderasan Naidoo, Fotini Sereti (2021)

Commentationes Mathematicae Universitatis Carolinae

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The universality problem focuses on finding universal spaces in classes of topological spaces. Moreover, in “Universal spaces and mappings” by S. D. Iliadis (2005), an important method of constructing such universal elements in classes of spaces is introduced and explained in details. Simultaneously, in “A topological dimension greater than or equal to the classical covering dimension” by D. N. Georgiou, A. C. Megaritis and F. Sereti (2017), new topological dimension is introduced and...

Levi's forms of higher codimensional submanifolds

Andrea D&#039;Agnolo, Giuseppe Zampieri (1991)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti Lincei. Matematica e Applicazioni

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Let $X ≅ C^{n}$ , let $M$ be a $C^{2}$ hypersurface of $X$ , $S$ be a $C^{2}$ submanifold of $M$ . Denote by $L_{M}$ the Levi form of $M$ at $z_{0} \in S$ . In a previous paper [3] two numbers $s^{\pm} (S, p)$ , $p \in {({\dot{T}}_{S}^{*} X)}_{z_{0}}$ are defined; for $S = M$ they are the numbers of positive and negative eigenvalues for $L_{M}$ . For $S \subset M$ , $p \in S \times_{M} \dot{T}^{*}_{S} X)$ , we show here that $s^{\pm} (S, p)$ are still the numbers of positive and negative eigenvalues for $L_{M}$ when restricted to $T_{z_{0}}^{C} S$ . Applications to the concentration in degree for microfunctions at the boundary are given.

Maps with dimensionally restricted fibers

Vesko Valov (2011)

Colloquium Mathematicae

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We prove that if f: X → Y is a closed surjective map between metric spaces such that every fiber $f^{- 1} (y)$ belongs to a class S of spaces, then there exists an $F_{σ}$ -set A ⊂ X such that A ∈ S and $d i m f^{- 1} (y) ∖ A = 0$ for all y ∈ Y. Here, S can be one of the following classes: (i) M: e-dim M ≤ K for some CW-complex K; (ii) C-spaces; (iii) weakly infinite-dimensional spaces. We also establish that if S = M: dim M ≤ n, then dim f ∆ g ≤ 0 for almost all $g \in C (X,^{n + 1})$ .

On dimensionally restricted maps

H. Murat Tuncali, Vesko Valov (2002)

Fundamenta Mathematicae

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Let f: X → Y be a closed n-dimensional surjective map of metrizable spaces. It is shown that if Y is a C-space, then: (1) the set of all maps g: X → ⁿ with dim(f △ g) = 0 is uniformly dense in C(X,ⁿ); (2) for every 0 ≤ k ≤ n-1 there exists an $F_{σ}$ -subset $A_{k}$ of X such that $d i m A_{k} \leq k$ and the restriction $f | (X ∖ A_{k})$ is (n-k-1)-dimensional. These are extensions of theorems by Pasynkov and Toruńczyk, respectively, obtained for finite-dimensional spaces. A generalization of a result due to Dranishnikov and Uspenskij...

Some results on Poincaré sets

Min-wei Tang, Zhi-Yi Wu (2020)

Czechoslovak Mathematical Journal

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It is known that a set $H$ of positive integers is a Poincaré set (also called intersective set, see I. Ruzsa (1982)) if and only if ${dim}_{ℋ} (X_{H}) = 0$ , where $X_{H} : = \{x = \sum_{n = 1}^{\infty} \frac{x_{n}}{2^{n}} : x_{n} \in {0, 1}, x_{n} x_{n + h} = 0 for all n \geq 1, h \in H\}$ and ${dim}_{ℋ}$ denotes the Hausdorff dimension (see C. Bishop, Y. Peres (2017), Theorem 2.5.5). In this paper we study the set $X_{H}$ by replacing $2$ with $b > 2$ . It is surprising that there are some new phenomena to be worthy of studying. We study them and give several examples to explain our results.

Homogeneity and non-coincidence of Hausdorff and box dimensions for subsets of ℝⁿ

Anders Nilsson, Peter Wingren (2007)

Studia Mathematica

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A class of subsets of ℝⁿ is constructed that have certain homogeneity and non-coincidence properties with respect to Hausdorff and box dimensions. For each triple (r,s,t) of numbers in the interval (0,n] with r < s < t, a compact set K is constructed so that for any non-empty subset U relatively open in K, we have $(d i m_{H} (U), {\underset{̲}{d i m}}_{B} (U), {\bar{d i m}}_{B} (U)) = (r, s, t)$ . Moreover, $2^{- n} \leq H^{r} (K) \leq 2 n^{r / 2}$ .

Universal acyclic resolutions for arbitrary coefficient groups

Michael Levin (2003)

Fundamenta Mathematicae

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We prove that for every compactum X and every integer n ≥ 2 there are a compactum Z of dimension ≤ n+1 and a surjective $U V^{n - 1}$ -map r: Z → X such that for every abelian group G and every integer k ≥ 2 such that $d i m_{G} X \leq k \leq n$ we have $d i m_{G} Z \leq k$ and r is G-acyclic.

Cofiniteness of torsion functors of cofinite modules

Reza Naghipour, Kamal Bahmanpour, Imaneh Khalili Gorji (2014)

Colloquium Mathematicae

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Let R be a Noetherian ring and I an ideal of R. Let M be an I-cofinite and N a finitely generated R-module. It is shown that the R-modules $T o r_{i}^{R} (N, M)$ are I-cofinite for all i ≥ 0 whenever dim Supp(M) ≤ 1 or dim Supp(N) ≤ 2. This immediately implies that if I has dimension one (i.e., dim R/I = 1) then the R-modules $T o r_{i}^{R} (N, H_{I}^{j} (M))$ are I-cofinite for all i,j ≥ 0. Also, we prove that if R is local, then the R-modules $T o r_{i}^{R} (N, M)$ are I-weakly cofinite for all i ≥ 0 whenever dim Supp(M) ≤ 2 or dim Supp(N) ≤ 3. Finally, it...

The canonical constructions of connections on total spaces of fibred manifolds

Włodzimierz M. Mikulski (2024)

Archivum Mathematicum

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We classify classical linear connections $A (Γ, Λ, Θ)$ on the total space $Y$ of a fibred manifold $Y \to M$ induced in a natural way by the following three objects: a general connection $Γ$ in $Y \to M$ , a classical linear connection $Λ$ on $M$ and a linear connection $Θ$ in the vertical bundle $V Y \to Y$ . The main result says that if $\dim (M) \geq 3$ and $\dim (Y) - \dim (M) \geq 3$ then the natural operators $A$ under consideration form the $17$ dimensional affine space.

Joint distribution for the Selmer ranks of the congruent number curves

Ilija S. Vrećica (2020)

Czechoslovak Mathematical Journal

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We determine the distribution over square-free integers $n$ of the pair $({dim}_{𝔽_{2}} {Sel}^{Φ} (E_{n} / ℚ), {dim}_{𝔽_{2}} {Sel}^{\hat{Φ}} (E_{n}^{'} / ℚ))$ , where $E_{n}$ is a curve in the congruent number curve family, $E_{n}^{'} : y^{2} = x^{3} + 4 n^{2} x$ is the image of isogeny $Φ : E_{n} \to E_{n}^{'}$ , $Φ (x, y) = (y^{2} / x^{2}, y (n^{2} - x^{2}) / x^{2})$ , and $\hat{Φ}$ is the isogeny dual to $Φ$ .

$ℰ_{B}$ -dimension function of bitopological spaces

M. Jelić (1987)

Matematički Vesnik

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On the Separation Dimension of $K_{ω}$

Yasunao Hattori, Jan van Mill (2013)

Bulletin of the Polish Academy of Sciences. Mathematics

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We prove that $t r t K_{ω} > ω + 1$ , where trt stands for the transfinite extension of Steinke’s separation dimension. This answers a question of Chatyrko and Hattori.

On the Hausdorff Dimension of Topological Subspaces

Tomasz Szarek, Maciej Ślęczka (2006)

Bulletin of the Polish Academy of Sciences. Mathematics

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It is shown that every Polish space X with $d i m_{T} X \geq d$ admits a compact subspace Y such that $d i m_{H} Y \geq d$ where $d i m_{T}$ and $d i m_{H}$ denote the topological and Hausdorff dimensions, respectively.

A finiteness theorem for holomorphic Banach bundles

Jürgen Leiterer (2007)

Annali della Scuola Normale Superiore di Pisa - Classe di Scienze

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Let $E$ be a holomorphic Banach bundle over a compact complex manifold, which can be defined by a cocycle of holomorphic transition functions with values of the form $id + K$ where $K$ is compact. Assume that the characteristic fiber of $E$ has the compact approximation property. Let $n$ be the complex dimension of $X$ and $0 \leq q \leq n$ . Then: If $V \to X$ is a holomorphic vector bundle (of finite rank) with $H^{q} (X, V) = 0$ , then $dim H^{q} (X, V \otimes E) < \infty$ . In particular, if $dim H^{q} (X, 𝒪) = 0$ , then $dim H^{q} (X, E) < \infty$ .