English

Completely nonmeasurable unions

Logic 2010-03-05 v1

Abstract

Assume that there is no quasi-measurable cardinal smaller than 2ω2^\omega. (κ\kappa is quasi measurable if there exists κ\kappa -additive ideal \ci\ci of subsets of κ\kappa such that the Boolean algebra P(κ)/\ciP(\kappa)/\ci satisfies c.c.c.) We show that for a c.c.c. σ\sigma -ideal I with a Borel base of subsets of an uncountable Polish space, if A\cal A is a point-finite family of subsets from I then there is an uncountable collection of pairwise disjoint subfamilies of A\cal A whose union is completely nonmeasurable i.e. its intersection with every non-small Borel set does not belong to the σ\sigma -field generated by Borel sets and the ideal I. This result is a generalization of Four Poles Theorem.

Keywords

Cite

@article{arxiv.1003.0918,
  title  = {Completely nonmeasurable unions},
  author = {Robert Ralowski and Szymon Zeberski},
  journal= {arXiv preprint arXiv:1003.0918},
  year   = {2010}
}

Comments

6 pages

R2 v1 2026-06-21T14:53:34.108Z