For a Tychonoff space $X$, let $\downarrow {\mathrm{C}}_F\left(X\right)$ be the family of hypographs of all continuous maps from $X$ to $[0,1]$ endowed with the Fell topology. It is proved that $X$ has a dense separable metrizable locally compact open subset if $\downarrow {\mathrm{C}}_F\left(X\right)$ is metrizable. Moreover, for a first-countable space $X$, $\downarrow {\mathrm{C}}_F\left(X\right)$ is metrizable if and only if $X$ itself is a locally compact separable metrizable space. There exists a Tychonoff space $X$ such that $\downarrow {\mathrm{C}}_F\left(X\right)$ is metrizable but $X$ is not first-countable.

The aim of the paper is to introduce and study a new class of spaces called mildly ${(1,2)}^{*}$-normal spaces and a new class of functions called ${(1,2)}^{*}$-$\mathrm{rg}$-continuous, ${(1,2)}^{*}$-$\mathrm{R}$-map, almost ${(1,2)}^{*}$-continuous function and almost ${(1,2)}^{*}$-$\mathrm{rg}$-closed function in bitopological spaces. Subsequently, the relationships between mildly ${(1,2)}^{*}$-normal spaces and the new bitopological functions are investigated. Moreover, we obtain characterizations of mildly ${(1,2)}^{*}$-normal spaces, properties of the new bitopological functions and preservation theorems for...

We prove that an ultrametric space can be bi-Lipschitz embedded in ${ℝ}^n$ if its metric dimension in Assouad’s sense is smaller than n. We also characterize ultrametric spaces up to bi-Lipschitz homeomorphism as dense subspaces of ultrametric inverse limits of certain inverse sequences of discrete spaces.

A minimax theorem is proved which contains a recent result of Pinelis and a version of the classical minimax theorem of Ky Fan as special cases. Some applications to the theory of convex metric spaces (farthest points, rendez-vous value) are presented.

In this survey we present two Mittag-Leffler lemmas and several applications to topics as varied as the delta-equation, Fréchet algebras, inductive limits of Banach spaces and quasi-normable Fréchet spaces.

We show that there exists an Abelian topological group $G$ such that the operations in $G$ cannot be extended to the Dieudonné completion $\mu G$ of the space $G$ in such a way that $G$ becomes a topological subgroup of the topological group $\mu G$. This provides a complete answer to a question of V.G. Pestov and M.G. Tkačenko, dating back to 1985. We also identify new large classes of topological groups for which such an extension is possible. The technique developed also allows to find many new solutions to the...

We define a metric $d_S$, called the shape metric, on the hyperspace $2^X$ of all non-empty compact subsets of a metric space X. Using it we prove that a compactum X in the Hilbert cube is movable if and only if X is the limit of a sequence of polyhedra in the shape metric. This fact is applied to show that the hyperspace $(2^{ℝ}2$, dS)$isseparable.Ontheotherhand,wegiveanexampleshowingthat$2ℝ2$isnotseparableinthefundamentalmetricintroducedbyBorsuk.$