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g * -closed sets and a new separation axiom in Alexandroff spaces

Pratulananda Das, Md. Mamun Ar Rashid (2003)

Archivum Mathematicum

In this paper we introduce the concept of g * -closed sets and investigate some of its properties in the spaces considered by A. D. Alexandroff [1] where only countable unions of open sets are required to be open. We also introduce a new separation axiom called T w -axiom in the Alexandroff spaces with the help of g * -closed sets and investigate some of its consequences.

g -metrizable spaces and the images of semi-metric spaces

Ying Ge, Shou Lin (2007)

Czechoslovak Mathematical Journal

In this paper, we prove that a space X is a g -metrizable space if and only if X is a weak-open, π and σ -image of a semi-metric space, if and only if X is a strong sequence-covering, quotient, π and m s s c -image of a semi-metric space, where “semi-metric” can not be replaced by “metric”.

Generalized analytic spaces, completeness and fragmentability

Petr Holický (2001)

Czechoslovak Mathematical Journal

Classical analytic spaces can be characterized as projections of Polish spaces. We prove analogous results for three classes of generalized analytic spaces that were introduced by Z. Frolík, D. Fremlin and R. Hansell. We use the technique of complete sequences of covers. We explain also some relations of analyticity to certain fragmentability properties of topological spaces endowed with an additional metric.

Generalized Helly spaces, continuity of monotone functions, and metrizing maps

Lech Drewnowski, Artur Michalak (2008)

Fundamenta Mathematicae

Given an ordered metric space (in particular, a Banach lattice) E, the generalized Helly space H(E) is the set of all increasing functions from the interval [0,1] to E considered with the topology of pointwise convergence, and E is said to have property (λ) if each of these functions has only countably many points of discontinuity. The main objective of the paper is to study those ordered metric spaces C(K,E), where K is a compact space, that have property (λ). In doing so, the guiding idea comes...

Generalized linearly ordered spaces and weak pseudocompactness

Oleg Okunev, Angel Tamariz-Mascarúa (1997)

Commentationes Mathematicae Universitatis Carolinae

A space X is truly weakly pseudocompact if X is either weakly pseudocompact or Lindelöf locally compact. We prove that if X is a generalized linearly ordered space, and either (i) each proper open interval in X is truly weakly pseudocompact, or (ii) X is paracompact and each point of X has a truly weakly pseudocompact neighborhood, then X is truly weakly pseudocompact. We also answer a question about weakly pseudocompact spaces posed by F. Eckertson in [Eck].

Geometry of compactifications of locally symmetric spaces

Lizhen Ji, Robert Macpherson (2002)

Annales de l’institut Fourier

For a locally symmetric space M , we define a compactification M M ( ) which we call the “geodesic compactification”. It is constructed by adding limit points in M ( ) to certain geodesics in M . The geodesic compactification arises in other contexts. Two general constructions of Gromov for an ideal boundary of a Riemannian manifold give M ( ) for locally symmetric spaces. Moreover, M ( ) has a natural group theoretic construction using the Tits building. The geodesic compactification plays two fundamental roles in...

Currently displaying 641 – 660 of 1977