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Adding machines, endpoints, and inverse limit spaces

Lori Alvin, Karen Brucks (2010)

Fundamenta Mathematicae

Let f be a unimodal map in the logistic or symmetric tent family whose restriction to the omega limit set of the turning point is topologically conjugate to an adding machine. A combinatoric characterization is provided for endpoints of the inverse limit space (I,f), where I denotes the core of the map.

Addition theorems and D -spaces

Aleksander V. Arhangel'skii, Raushan Z. Buzyakova (2002)

Commentationes Mathematicae Universitatis Carolinae

It is proved that if a regular space X is the union of a finite family of metrizable subspaces then X is a D -space in the sense of E. van Douwen. It follows that if a regular space X of countable extent is the union of a finite collection of metrizable subspaces then X is Lindelöf. The proofs are based on a principal result of this paper: every space with a point-countable base is a D -space. Some other new results on the properties of spaces which are unions of a finite collection of nice subspaces...

Addition theorems, D -spaces and dually discrete spaces

Ofelia Teresa Alas, Vladimir Vladimirovich Tkachuk, Richard Gordon Wilson (2009)

Commentationes Mathematicae Universitatis Carolinae

A neighbourhood assignment in a space X is a family 𝒪 = { O x : x X } of open subsets of X such that x O x for any x X . A set Y X is a kernel of 𝒪 if 𝒪 ( Y ) = { O x : x Y } = X . If every neighbourhood assignment in X has a closed and discrete (respectively, discrete) kernel, then X is said to be a D -space (respectively a dually discrete space). In this paper we show among other things that every GO-space is dually discrete, every subparacompact scattered space and every continuous image of a Lindelöf P -space is a D -space and we prove an addition...

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