REPOZYTORIUM UNIWERSYTETU
W BIAŁYMSTOKU

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 Tytuł: Topological Manifolds Autorzy: Pąk, Karol Słowa kluczowe: locally Euclidean spacesinteriorboundaryCartesian product Data wydania: 2014 Data dodania: 9-gru-2015 Wydawca: De Gruyter Open Źródło: Formalized Mathematics, Volume 22, Issue 2, 2014, Pages 179-186 Abstrakt: Let us recall that a topological space M is a topological manifold if M is second-countable Hausdorff and locally Euclidean, i.e. each point has a neighborhood that is homeomorphic to an open ball of E n for some n. However, if we would like to consider a topological manifold with a boundary, we have to extend this definition. Therefore, we introduce here the concept of a locally Euclidean space that covers both cases (with and without a boundary), i.e. where each point has a neighborhood that is homeomorphic to a closed ball of En for some n. Our purpose is to prove, using the Mizar formalism, a number of properties of such locally Euclidean spaces and use them to demonstrate basic properties of a manifold. Let T be a locally Euclidean space. We prove that every interior point of T has a neighborhood homeomorphic to an open ball and that every boundary point of T has a neighborhood homeomorphic to a closed ball, where additionally this point is transformed into a point of the boundary of this ball. When T is n-dimensional, i.e. each point of T has a neighborhood that is homeomorphic to a closed ball of En, we show that the interior of T is a locally Euclidean space without boundary of dimension n and the boundary of T is a locally Euclidean space without boundary of dimension n − 1. Additionally, we show that every connected component of a compact locally Euclidean space is a locally Euclidean space of some dimension. We prove also that the Cartesian product of locally Euclidean spaces also forms a locally Euclidean space. We determine the interior and boundary of this product and show that its dimension is the sum of the dimensions of its factors. At the end, we present several consequences of these results for topological manifolds. This article is based on [14]. Afiliacja: Institute of Informatics University of Białystok Sosnowa 64, 15-887 Białystok Poland Sponsorzy: The paper has been financed by the resources of the Polish National Science Centre granted by decision no. DEC-2012/07/N/ST6/02147. URI: http://hdl.handle.net/11320/3715 DOI: 10.2478/forma-2014-0019 ISSN: 1426-26301898-9934 Typ Dokumentu: Article Występuje w kolekcji(ach): Artykuły naukowe (IInf)Formalized Mathematics, 2014, Volume 22, Issue 2

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