Non-separating subcontinua of planar continua
We revisit an old question of Knaster by demonstrating that each non-degenerate plane hereditarily unicoherent continuum X contains a proper, non-degenerate subcontinuum which does not separate X.
We revisit an old question of Knaster by demonstrating that each non-degenerate plane hereditarily unicoherent continuum X contains a proper, non-degenerate subcontinuum which does not separate X.
Si dimostra con esempi che la distanza di Hausdorff-Carathéodory fra i valori di funzioni multivoche, analitiche secondo Oka, non è subarmonica.
We establish that for a fairly general class of topologically transitive dynamical systems, the set of non-transitive points is very small when the rate of transitivity is very high. The notion of smallness that we consider here is that of σ-porosity, and in particular we show that the set of non-transitive points is σ-porous for any subshift that is a factor of a transitive subshift of finite type, and for the tent map of [0,1]. The result extends to some finite-to-one factor systems. We also show...
We prove that if 𝓒 is a family of separable Banach spaces which is analytic with respect to the Effros Borel structure and no X ∈ 𝓒 is isometrically universal for all separable Banach spaces, then there exists a separable Banach space with a monotone Schauder basis which is isometrically universal for 𝓒 but not for all separable Banach spaces. We also establish an analogous result for the class of strictly convex spaces.
Let be a Baire space, be a compact Hausdorff space and be a quasi-continuous mapping. For a proximal subset of we will use topological games and on between two players to prove that if the first player has a winning strategy in these games, then is norm continuous on a dense subset of . It follows that if is Valdivia compact, each quasi-continuous mapping from a Baire space to is norm continuous on a dense subset of .
Let be the class of Banach spaces X for which every weakly quasi-continuous mapping f: A → X defined on an α-favorable space A is norm continuous at the points of a dense subset of A. We will show that this class is stable under c₀-sums and -sums of Banach spaces for 1 ≤ p < ∞.
Let , where is a measurable space, and a topological space. We study inclusions between three classes of extended real-valued functions on which are upper semicontinuous in and satisfy some measurability conditions.