Displaying similar documents to “Where are typical C 1 functions one-to-one?”

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 ) , d i m ̲ B ( U ) , d i m ¯ B ( U ) ) = ( r , s , t ) . Moreover, 2 - n H r ( K ) 2 n r / 2 .

A poset of topologies on the set of real numbers

Vitalij A. Chatyrko, Yasunao Hattori (2013)

Commentationes Mathematicae Universitatis Carolinae

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On the set of real numbers we consider a poset 𝒫 τ ( ) (by inclusion) of topologies τ ( A ) , where A , such that A 1 A 2 iff τ ( A 1 ) τ ( A 2 ) . The poset has the minimal element τ ( ) , the Euclidean topology, and the maximal element τ ( ) , the Sorgenfrey topology. We are interested when two topologies τ 1 and τ 2 (especially, for τ 2 = τ ( ) ) from the poset define homeomorphic spaces ( , τ 1 ) and ( , τ 2 ) . In particular, we prove that for a closed subset A of the space ( , τ ( A ) ) is homeomorphic to the Sorgenfrey line ( , τ ( ) ) iff A is countable. We study also common...

Compacta are maximally G δ -resolvable

István Juhász, Zoltán Szentmiklóssy (2013)

Commentationes Mathematicae Universitatis Carolinae

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It is well-known that compacta (i.e. compact Hausdorff spaces) are maximally resolvable, that is every compactum X contains Δ ( X ) many pairwise disjoint dense subsets, where Δ ( X ) denotes the minimum size of a non-empty open set in X . The aim of this note is to prove the following analogous result: Every compactum X contains Δ δ ( X ) many pairwise disjoint G δ -dense subsets, where Δ δ ( X ) denotes the minimum size of a non-empty G δ set in X .

Indiscernibles and dimensional compactness

C. Ward Henson, Pavol Zlatoš (1996)

Commentationes Mathematicae Universitatis Carolinae

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This is a contribution to the theory of topological vector spaces within the framework of the alternative set theory. Using indiscernibles we will show that every infinite set u S G in a biequivalence vector space W , M , G , such that x - y M for distinct x , y u , contains an infinite independent subset. Consequently, a class X G is dimensionally compact iff the π -equivalence M is compact on X . This solves a problem from the paper [NPZ 1992] by J. Náter, P. Pulmann and the second author.