An archimedean vector lattice A might have the following properties: (1) the sigma property (σ): For each ${aₙ}_{n\in \mathbb{N}}conA⁺$ there are ${\lambda ₙ}_{n\in \mathbb{N}}\subseteq (0,\infty )$ and a ∈ A with λₙaₙ ≤ a for each n; (2) order convergence and relative uniform convergence are equivalent, denoted (OC ⇒ RUC): if aₙ ↓ 0 then aₙ → 0 r.u. The conjunction of these two is called strongly Egoroff. We consider vector lattices of the form D(X) (all extended real continuous functions on the compact space X) showing that (σ) and (OC ⇒ RUC) are equivalent, and equivalent...

À tout espace de Banach fonctionnel réticulé est associée une quasi-topologie. Avec une hypothèse de dénombrabilité convenable, cette notion généralise la topologie polonaise classique. Les ensembles singuliers sont les ensembles discrets, clairsemés etc. que l’on caractérise à l’aide des mesures qu’ils portent. Le théorème de Baire admet aussi une généralisation. Application est faite au modèle probabiliste et à la théorie du potentiel.

We show that some classes of small sets are topological versions of some combinatorial properties. We also give a characterization of spaces for which White has a winning strategy in the point-open game. We show that every Lusin set is undetermined, which solves a problem of Galvin.

A subspace A of a topological space X is said to be $P^{\gamma }$-embedded ($P^{\gamma }$(point-finite)-embedded) in X if every (point-finite) partition of unity α on A with |α| ≤ γ extends to a (point-finite) partition of unity on X. The main results are: (Theorem A) A subspace A of X is $P^{\gamma }$(point-finite)-embedded in X iff it is $P^{\gamma }$-embedded and every countable intersection B of cozero-sets in X with B ∩ A = ∅ can be separated from A by a cozero-set in X. (Theorem B) The product A × [0,1] is $P^{\gamma }$(point-finite)-embedded in X...

We study extension operators between spaces of continuous functions on the spaces $\sigma ₙ\left(2^X\right)$ of subsets of X of cardinality at most n. As an application, we show that if $B_H$ is the unit ball of a nonseparable Hilbert space H equipped with the weak topology, then, for any 0 < λ < μ, there is no extension operator $T:C\left(\lambda B_H\right)\to C\left(\mu B_H\right)$.

We prove an abstract version of the Kuratowski extension theorem for Borel measurable maps of a given class. It enables us to deduce and improve its nonseparable version due to Hansell. We also study the ranges of not necessarily injective Borel bimeasurable maps f and show that some control on the relative classes of preimages and images of Borel sets under f enables one to get a bound on the absolute class of the range of f. This seems to be of some interest even within separable spaces.

We show that, whenever $\Gamma$ is a countable abelian group and $\Delta$ is a finitely-generated subgroup of $\Gamma$, a generic measure-preserving action of $\Delta$ on a standard atomless probability space $(X,\mu )$ extends to a free measure-preserving action of $\Gamma$ on $(X,\mu )$. This extends a result of Ageev, corresponding to the case when $\Delta$ is infinite cyclic.

A class of closed, bounded, convex sets in the Banach space $c_0$ is shown to be a complete PCA set.