We prove that the maximal Hausdorff compactification χf of a T2-compactifiable mapping f and the maximal Tychonoff compactification βf 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 T2-compactifiable (respectively, of a Tychonoff) mapping, which is a generalization of...

We continue Mizar formalization of General Topology according to the book [20] by Engelking. Niemytzki plane is defined as halfplane y ≥ 0 with topology introduced by a neighborhood system. Niemytzki plane is not T4. Next, the definition of Tychonoff space is given. The characterization of Tychonoff space by prebasis and the fact that Tychonoff spaces are between T3 and T4 is proved. The final ...

In this paper, we prove the following two statements: (1) There exists a discretely absolutely star-Lindelöf Tychonoff space having a regular-closed subspace which is not CCC-Lindelöf. (2) Every Hausdorff (regular, Tychonoff) linked-Lindelöf space can be represented in a Hausdorff (regular, Tychonoff) absolutely star-Lindelöf space as a closed Gδ subspace.

2.1. Basic properties: separation, countability, separability, compactness, connectedness. A space X is Tychonoff if for u, v ∈ X, there exists a neighborhood of u not containing v (and by symmetry a neighborhood of v not containing u). It is Hausdorff if every two points can be separated by disjoint neighborhoods. It is regular if it is Tychonoff and every closed set and point not in the set c...

This is a continuation of [dhhkr]. We study the Tychonoff Compactness Theorem for various definitions of compact and for various types of spaces, (first and second countable spaces, Hausdorff spaces, and subspaces of R). We also study well ordered Tychonoff products and the effect that the multiple choice axiom has on such products.

After introducing many different types of prefilter convergence, we introduce an universal method to define various notions of compactness using cluster point and convergence of a prefilter and to prove the Tychonoff theorem using characterizations of ultra(maximal) prefilters. : prefilter convergence, universal method, Tychonoff theorem, ultra prefilter, good extension

Given an uncountable cardinal א, the product space I, I = [0, 1], is called a Tychonoff cube. A collection of closed subsets of a subspace Y of a Tychonoff cube I that covers Y determines a weak topology for Y . The collection of compact subsets of I that have a countable dense subset covers I. It is known from work of the author and I. Ivanšić that the weak topology generated by this collectio...

We introduce a new kind of cover called a normal isolator cover to characterize maximal Tychonoff spaces. Such a study is used to provide an alternative proof of an interesting result of Feng and Garcia-Ferreira in 1999 that every maximal Tychonoff space is extremally disconnected. Maximal tychonoffness of subspaces is also discussed.