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Openly factorizable spaces and compact extensions of topological semigroups

Taras O. Banakh, Svetlana Dimitrova (2010)

Commentationes Mathematicae Universitatis Carolinae

We prove that the semigroup operation of a topological semigroup S extends to a continuous semigroup operation on its Stone-Čech compactification β S provided S is a pseudocompact openly factorizable space, which means that each map f : S Y to a second countable space Y can be written as the composition f = g p of an open map p : X Z onto a second countable space Z and a map g : Z Y . We present a spectral characterization of openly factorizable spaces and establish some properties of such spaces.

Ordered Cauchy spaces.

Kent, Darrell C., Vainio, R. (1985)

International Journal of Mathematics and Mathematical Sciences

Ordinal remainders of classical ψ-spaces

Alan Dow, Jerry E. Vaughan (2012)

Fundamenta Mathematicae

Let ω denote the set of natural numbers. We prove: for every mod-finite ascending chain T α : α < λ of infinite subsets of ω, there exists [ ω ] ω , an infinite maximal almost disjoint family (MADF) of infinite subsets of the natural numbers, such that the Stone-Čech remainder βψ∖ψ of the associated ψ-space, ψ = ψ(ω,ℳ ), is homeomorphic to λ + 1 with the order topology. We also prove that for every λ < ⁺, where is the tower number, there exists a mod-finite ascending chain T α : α < λ , hence a ψ-space with Stone-Čech remainder...

Perfect compactifications of frames

Dharmanand Baboolal (2011)

Czechoslovak Mathematical Journal

Perfect compactifications of frames are introduced. It is shown that the Stone-Čech compactification is an example of such a compactification. We also introduce rim-compact frames and for such frames we define its Freudenthal compactification, another example of a perfect compactification. The remainder of a rim-compact frame in its Freudenthal compactification is shown to be zero-dimensional. It is shown that with the assumption of the Boolean Ultrafilter Theorem the Freudenthal compactification...

Perfect compactifications of functions

Giorgio Nordo, Boris A. Pasynkov (2000)

Commentationes Mathematicae Universitatis Carolinae

We prove that the maximal Hausdorff compactification χ f of a T 2 -compactifiable mapping f and the maximal Tychonoff compactification β f of a Tychonoff mapping f (see [P]) are perfect. This allows us to give a characterization of all perfect Hausdorff (respectively, all perfect Tychonoff) compactifications of a T 2 -compactifiable (respectively, of a Tychonoff) mapping, which is a generalization of two results of Skljarenko [S] for the Hausdorff compactifications of Tychonoff spaces.

Perfect mappings in topological groups, cross-complementary subsets and quotients

Aleksander V. Arhangel'skii (2003)

Commentationes Mathematicae Universitatis Carolinae

The following general question is considered. Suppose that G is a topological group, and F , M are subspaces of G such that G = M F . Under these general assumptions, how are the properties of F and M related to the properties of G ? For example, it is observed that if M is closed metrizable and F is compact, then G is a paracompact p -space. Furthermore, if M is closed and first countable, F is a first countable compactum, and F M = G , then G is also metrizable. Several other results of this kind are obtained....

Perfectness of the Higson and Smirnov compactifications

Yuji Akaike, Naotsugu Chinen, Kazuo Tomoyasu (2007)

Colloquium Mathematicae

We provide a necessary and sufficient condition for the Higson compactification to be perfect for the noncompact, locally connected, proper metric spaces. We also discuss perfectness of the Smirnov compactification.

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