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Regular spaces of small extent are ω-resolvable

István Juhász, Lajos Soukup, Zoltán Szentmiklóssy (2015)

Fundamenta Mathematicae

We improve some results of Pavlov and Filatova, concerning a problem of Malykhin, by showing that every regular space X that satisfies Δ(X) > e(X) is ω-resolvable. Here Δ(X), the dispersion character of X, is the smallest size of a non-empty open set in X, and e(X), the extent of X, is the supremum of the sizes of all closed-and-discrete subsets of X. In particular, regular Lindelöf spaces of uncountable dispersion character are ω-resolvable. We also prove that any regular...

Relative symmetrizability and metrizability

Aleksander V. Arhangel'skii, I. Ju. Gordienko (1996)

Commentationes Mathematicae Universitatis Carolinae

Relative metrizability is defined and connections with other relative properties are established.

Relatively coarse sequential convergence

Roman Frič, Fabio Zanolin (1997)

Czechoslovak Mathematical Journal

We generalize the notion of a coarse sequential convergence compatible with an algebraic structure to a coarse one in a given class of convergences. In particular, we investigate coarseness in the class of all compatible convergences (with unique limits) the restriction of which to a given subset is fixed. We characterize such convergences and study relative coarseness in connection with extensions and completions of groups and rings. E.g., we show that: (i) each relatively coarse dense group precompletion...

Relatively maximal convergences

Szymon Dolecki, Michel Pillot (1998)

Bollettino dell'Unione Matematica Italiana

Topologie, pretopologie, paratopologie e pseudotopologie sono importanti classi di convergenze, chiuse per estremi superiori (superiormente chiuse) ed inoltre caratterizzabili mediante le aderenze di certi filtri. Convergenze J -massimali in una classe superiormente chiusa D J , cioè massimali fra le D -convergenze aventi la stessa imagine per la proiezione su J , svolgono un ruolo importante nella teoria dei quozienti; infatti, una mappa J -quoziente sulla convergenza J -massimale in D è automaticamente...

Remainders of metrizable and close to metrizable spaces

A. V. Arhangel'skii (2013)

Fundamenta Mathematicae

We continue the study of remainders of metrizable spaces, expanding and applying results obtained in [Fund. Math. 215 (2011)]. Some new facts are established. In particular, the closure of any countable subset in the remainder of a metrizable space is a Lindelöf p-space. Hence, if a remainder of a metrizable space is separable, then this remainder is a Lindelöf p-space. If the density of a remainder Y of a metrizable space does not exceed 2 ω , then Y is a Lindelöf Σ-space. We also show that many of...

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