Unbouded descending infinite chain in Rudin-Frolík order
We give two examples of tent maps with uncountable (as it happens, post-critical) ω-limit sets, which have isolated points, with interesting structures. Such ω-limit sets must be of the form C ∪ R, where C is a Cantor set and R is a scattered set. Firstly, it is known that there is a restriction on the topological structure of countable ω-limit sets for finite-to-one maps satisfying at least some weak form of expansivity. We show that this restriction does not hold if the ω-limit set is uncountable....
There is a disk in S3 whose interior is PL embedded and whose boundary has a tame Cantor set of locally wild points, such that the n-fold cyclic coverings of S3 branched over the boundary of the disk are all S3. An uncountable set of inequivalent wild knots with these properties is exhibited.
We show that a set of reals is undetermined in Galvin's point-open game iff it is uncountable and has property C", which answers a question of Gruenhage.
We prove that a metric space is an ANR if, and only if, every open subset of X has the homotopy type of a CW-complex.
Dans cet article, on développe, pour les espaces paracompacts, une méthode de construction analogue à la construction par récurrence sur les squelettes dans les -complexes. On l’applique à des problèmes de prolongement ainsi qu’à l’existence de fonctions canoniques dans les nerfs de recouvrements fermés.