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A well known theorem of W.W. Comfort and K.A. Ross, stating that every pseudocompact group is -embedded in its Weil completion [5] (which is a compact group), is extended to some new classes of topological groups, and the proofs are very transparent, short and elementary (the key role in the proofs belongs to Lemmas 1.1 and 4.1). In particular, we introduce a new notion of canonical uniform tightness of a topological group and prove that every -dense subspace of a topological group , such...
We show that every abelian Polish group is the topological factor group of a closed subgroup of the full unitary group of a separable Hilbert space with the strong operator topology. It follows that all orbit equivalence relations induced by abelian Polish group actions are Borel reducible to some orbit equivalence relations induced by actions of the unitary group.
The notion of -convergence of a sequence of functions is stronger than pointwise convergence and weaker than uniform convergence. It is inspired by the investigation of ill-posed problems done by A.N. Tichonov. We answer a question posed by M. Katětov around 1970 by showing that the only analytic metric spaces for which pointwise convergence of a sequence of continuous real valued functions to a (continuous) limit function on implies -convergence are -compact spaces. We show that the assumption...
Absolute stability of a compact set is characterized by the cardinality of a fundamental system of positively invariant neighborhoods.
We prove that a cosmic space (= a Tychonoff space with a countable network) is analytic if it is an image of a -analytic space under a measurable mapping. We also obtain characterizations of analyticity and -compactness in cosmic spaces in terms of metrizable continuous images. As an application, we show that if is a separable metrizable space and is its dense subspace then the space of restricted continuous functions is analytic iff it is a -space iff is -compact.
We continue the study of topological properties of the group Homeo(X) of all homeomorphisms of a Cantor set X with respect to the uniform topology τ, which was started by Bezuglyi, Dooley, Kwiatkowski and Medynets. We prove that the set of periodic homeomorphisms is τ-dense in Homeo(X) and deduce from this result that the topological group (Homeo(X),τ) has the Rokhlin property, i.e., there exists a homeomorphism whose conjugacy class is τ-dense in Homeo(X). We also show that for any homeomorphism...
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