Poznámka o řídkých množinách v
Product decomposition of a -ring
Products of ideals of Borel sets
Products of non--lower porous sets
In the present article we provide an example of two closed non--lower porous sets such that the product is lower porous. On the other hand, we prove the following: Let and be topologically complete metric spaces, let be a non--lower porous Suslin set and let be a non--porous Suslin set. Then the product is non--lower porous. We also provide a brief summary of some basic properties of lower porosity, including a simple characterization of Suslin non--lower porous sets in topologically...
Properties of a function of E. Marczewski
Properties of measure and category in generalized Cohen's and Silver's forcing
Radon spaces which are not -fragmentable
Ramsey, Lebesgue, and Marczewski sets and the Baire property
We investigate the completely Ramsey, Lebesgue, and Marczewski σ-algebras and their relations to the Baire property in the Ellentuck and density topologies. Two theorems concerning the Marczewski σ-algebra (s) are presented. THEOREM. In the density topology D, (s) coincides with the σ-algebra of Lebesgue measurable sets. THEOREM. In the Ellentuck topology on , is a proper subset of the hereditary ideal associated with (s). We construct an example in the Ellentuck topology of a set which is...
Relations between Shy Sets and Sets of -Measure Zero in Solovay’s Model
An example of a non-zero non-atomic translation-invariant Borel measure on the Banach space is constructed in Solovay’s model. It is established that, for 1 ≤ p < ∞, the condition "-almost every element of has a property P" implies that “almost every” element of (in the sense of [4]) has the property P. It is also shown that the converse is not valid.
Remark on completely Baire-additive families in analytic spaces
Remarks on density topology and its category analogue
Remarks on products of σ-ideals
Remarks on the structure of tt-degrees based on constructive measure theory
Remarks on vector sums of Borel sets
Remarks on -fields without continuous measure
Remarks on σ-fields without continuous measures
Rudin-like sets and hereditary families of compact sets
We show that a comeager Π₁¹ hereditary family of compact sets must have a dense subfamily which is also hereditary. Using this, we prove an “abstract” result which implies the existence of independent ℳ ₀-sets, the meagerness of ₀-sets with the property of Baire, and generalizations of some classical results of Mycielski. Finally, we also give some natural examples of true sets.
Selections using orderings (non-separable case)
Semiring of Sets
Schmets [22] has developed a measure theory from a generalized notion of a semiring of sets. Goguadze [15] has introduced another generalized notion of semiring of sets and proved that all known properties that semiring have according to the old definitions are preserved. We show that this two notions are almost equivalent. We note that Patriota [20] has defined this quasi-semiring. We propose the formalization of some properties developed by the authors.
Semiring of Sets: Examples
This article proposes the formalization of some examples of semiring of sets proposed by Goguadze [8] and Schmets [13].