T...-Abgeschlossenheit und T...-Minimalität.
An Example in Category Theory.
Fortsetzbarkeit stetiger Abbildungen und Kompaktheitsgrad topologischer Räume.
Nicht alle T2-minimalen Räume sind von 2. Kategorie.
Wann sind alle stetigen Abbildungen in Y konstant?
...-kompakte Räume.
Factorizations of Morphisms f: B... FA.
Initial Completions.
A characterization of K-ary algebraic categories.
On the failure of Birkhoff's theorem for locally small based equational categories of algebras
Quotienten geordneter Räume und Folgenkonvergenz
Ordnungsfähigkeit zusammenhängender Räume
Reflective Mac Neille completions of fibre-small categories need not be fibre-small
Epireflective subcategories of TOP need not be cowell-powered
Realizations of topologies and closure operators by set systems and by neighbourhoods
Sequential structures induced by merotopies
Choice principles in elementary topology and analysis
Many fundamental mathematical results fail in , i.e., in Zermelo-Fraenkel set theory without the Axiom of Choice. This article surveys results — old and new — that specify how much “choice” is needed to validate each of certain basic analytical and topological results.
Products of Lindelöf -spaces are Lindelöf – in some models of ZF
The stability of the Lindelöf property under the formation of products and of sums is investigated in ZF (= Zermelo-Fraenkel set theory without AC, the axiom of choice). It is • not surprising that countable summability of the Lindelöf property requires some weak choice principle, • highly surprising, however, that productivity of the Lindelöf property is guaranteed by a drastic failure of AC, • amusing that finite summability of the Lindelöf property takes place if either some weak choice principle...
Composing special epimorphisms and retractions
Coreflective subcategories in general topology
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