Displaying 21 – 40 of 56

Showing per page

Poincaré's recurrence theorem for set-valued dynamical systems

Jean-Pierre Aubin, Hélène Frankowska, Andrzej Lasota (1991)

Annales Polonici Mathematici

 Abstract. The existence theorem of an invariant measure and Poincare's Recurrence Theorem are extended to set-valued dynamical systems with closed graph on a compact metric space.

Points with maximal Birkhoff average oscillation

Jinjun Li, Min Wu (2016)

Czechoslovak Mathematical Journal

Let f : X X be a continuous map with the specification property on a compact metric space X . We introduce the notion of the maximal Birkhoff average oscillation, which is the “worst” divergence point for Birkhoff average. By constructing a kind of dynamical Moran subset, we prove that the set of points having maximal Birkhoff average oscillation is residual if it is not empty. As applications, we present the corresponding results for the Birkhoff averages for continuous functions on a repeller and locally...

Pointwise convergence and the Wadge hierarchy

Alessandro Andretta, Alberto Marcone (2001)

Commentationes Mathematicae Universitatis Carolinae

We show that if X is a Σ 1 1 separable metrizable space which is not σ -compact then C p * ( X ) , the space of bounded real-valued continuous functions on X with the topology of pointwise convergence, is Borel- Π 1 1 -complete. Assuming projective determinacy we show that if X is projective not σ -compact and n is least such that X is Σ n 1 then C p ( X ) , the space of real-valued continuous functions on X with the topology of pointwise convergence, is Borel- Π n 1 -complete. We also prove a simultaneous improvement of theorems of Christensen...

Preservation of the Borel class under open-LC functions

Alexey Ostrovsky (2011)

Fundamenta Mathematicae

Let X be a Borel subset of the Cantor set C of additive or multiplicative class α, and f: X → Y be a continuous function onto Y ⊂ C with compact preimages of points. If the image f(U) of every clopen set U is the intersection of an open and a closed set, then Y is a Borel set of the same class α. This result generalizes similar results for open and closed functions.

Productivity of coreflective classes of topological groups

Horst Herrlich, Miroslav Hušek (1999)

Commentationes Mathematicae Universitatis Carolinae

Every nontrivial countably productive coreflective subcategory of topological linear spaces is κ -productive for a large cardinal κ (see [10]). Unlike that case, in uniform spaces for every infinite regular cardinal κ , there are coreflective subcategories that are κ -productive and not κ + -productive (see [8]). From certain points of view, the category of topological groups lies in between those categories above and we shall show that the corresponding results on productivity of coreflective subcategories...

Currently displaying 21 – 40 of 56