Cluster sets of arbitrary functions defined on plane sets
Construction of an Uncountable Difference between Φ(B) and
We construct a set B and homeomorphism f where f and have property N such that the symmetric difference between the sets of density points and of f-density points of B is uncountable.
Constructive irrational space.
Continuity and theorem of Heine-Cantor.
Convergences for the group of real numbers
Covering Property Axiom and its consequences
We formulate a Covering Property Axiom , which holds in the iterated perfect set model, and show that it implies easily the following facts. (a) For every S ⊂ ℝ of cardinality continuum there exists a uniformly continuous function g: ℝ → ℝ with g[S] = [0,1]. (b) If S ⊂ ℝ is either perfectly meager or universally null then S has cardinality less than . (c) cof() = ω₁ < , i.e., the cofinality of the measure ideal is ω₁. (d) For every uniformly bounded sequence of Borel functions there are sequences:...