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Let $M$ be an ANR space and $X$ be a homotopy dense subspace in $M$. Assume that $M$ admits a continuous binary operation $*:Mtimes Mto M$ such that for every $x,yin M$ the inclusion $x*yin X$ holds if and only if $x,yin X$. Assume also that there exist continuous unary operations $u,v:Mto M$ such that $x=u(x)*v(x)$ for all $xin M$. Given a $2^omega$-stable $mathbf Pi^0_2$-hereditary weakly $mathbf Sigma^0_2$-additive class of spaces $mathcal C$, we prove that the pair $(M,X)$ is strongly $(mathbf Pi^0_1capmathcal C,mathcal C)$-universal if and only if for any compact space $Kinmathcal C$, subspace $Cinmathcal C$ of $K$ and nonempty open set $Usubseteq M$ there exists a continuous map $f:Kto U$ such that $f^{-1}[X]=C$. This characterization is applied to detecting strongly universal Lawson semilattices.
Assuming the existence of $mathfrak c$ incomparable selective ultrafilters, we classify the non-torsion Abelian groups of cardinality $mathfrak c$ that admit a countably compact group topology. We show that for each $kappa in [mathfrak c, 2^mathfrak
With a complete Heyting algebra $L$ as the truth value table, we prove that the collections of open filters of stratified $L$-valued topological spaces form a monad. By means of $L$-Scott topology and the specialization $L$-order, we get that the alg
A topological gyrogroup is a gyrogroup endowed with a topology such that the binary operation is jointly continuous and the inverse mapping is also continuous. In this paper, it is proved that if $G$ is a sequential topological gyrogroup with an $ome
The structure of topological spaces is analysed here through the lenses of fibrous preorders. Each topological space has an associated fibrous preorder and those fibrous preorders which return a topological space are called spacial. A special class o
The range of a trigonometric polynomial with complex coefficients can be interpreted as the image of the unit circle under a Laurent polynomial. We show that this range is contained in a real algebraic subset of the complex plane. Although the contai