Marczewski sets, measure and the Baire property
Measurability of equivalence classes and MEC-property in metric spaces.
Measurability of some sets of Borel measurable functions on .
Measurable functionals on function spaces
We prove that all measurable functionals on certain function spaces are measures; this improves the (known) results about weak sequential completeness of spaces of measures. As an application, we prove several results of this form: if the space of invariant functionals on a function space is separable then every invariant functional is a measure.
Measurable uniform spaces
Metric spaces admitting only trivial weak contractions
If (X,d) is a metric space then a map f: X → X is defined to be a weak contraction if d(f(x),f(y)) < d(x,y) for all x,y ∈ X, x ≠ y. We determine the simplest non-closed sets X ⊆ ℝⁿ in the sense of descriptive set-theoretic complexity such that every weak contraction f: X → X is constant. In order to do so, we prove that there exists a non-closed set F ⊆ ℝ such that every weak contraction f: F → F is constant. Similarly, there exists a non-closed set G ⊆ ℝ such that every weak contraction...
Metric spaces in which a strengthened form of Blumberg's theorem holds
Metric-fine, proximally fine, and locally fine uniform spaces
More Lusin properties in the product space
More on sg-compact spaces.
Multiapplications boréliennes à valeurs convexes de
n-Arc connected spaces
A space is n-arc connected (n-ac) if any family of no more than n-points are contained in an arc. For graphs the following are equivalent: (i) 7-ac, (ii) n-ac for all n, (iii) continuous injective image of a closed subinterval of the real line, and (iv) one of a finite family of graphs. General continua that are ℵ₀-ac are characterized. The complexity of characterizing n-ac graphs for n = 2,3,4,5 is determined to be strictly higher than that of the stated characterization of 7-ac graphs.
Non-meager P-filters are countable dense homogeneous
We prove that if ℱ is a non-meager P-filter, then both ℱ and are countable dense homogeneous spaces.
Nonmeasurable algebraic sums of sets of reals
We present a theorem which generalizes some known theorems on the existence of nonmeasurable (in various senses) sets of the form X+Y. Some additional related questions concerning measure, category and the algebra of Borel sets are also studied.
Non-separable analytic spaces and measurability
Non-universal families of separable Banach spaces
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.
Norms on possibilities. II: More ccc ideals on .
Note on a theorem of S. Mercourakis about weakly -analytic Banach spaces
Note on decompositions of metrizable spaces I
Note on decompositions of metrizable spaces II