On the limit superior of analytic sets (Q1061122)
From MaRDI portal
| This is the item page for this Wikibase entity, intended for internal use and editing purposes. Please use this page instead for the normal view: On the limit superior of analytic sets |
scientific article; zbMATH DE number 3908424
| Language | Label | Description | Also known as |
|---|---|---|---|
| English | On the limit superior of analytic sets |
scientific article; zbMATH DE number 3908424 |
Statements
On the limit superior of analytic sets (English)
0 references
1984
0 references
\textit{M. Laczkovich} proved [Anal. Math. 3, 199-206 (1977; Zbl 0362.04001)] that if the sets \(A_ 0,A_ 1,..\). are Borel sets of reals such that for every infinite subsequence H, lim sup\(\{\) \(A_ j: j\in H\}\) is uncountable, then for an appropriate infinite subsequence H even the intersection of the \(A_ j's\) (j\(\in H)\) is uncountable. He also showed that under the continuum hypothesis there are (non-Borel) sets for which this does not hold. In this paper we extend the first result to analytic sets (in Polish spaces), show that under \(MA(\omega_ 1)\) it is true for any sets, but can be false with the cardinality of continuum 'anything'. Under the axiom of constructibility the statement is false for co-analytic sets. At the end of the paper a different proof for the analytic case is given: from the \(MA(\omega_ 1)\) result using absoluteness.
0 references
Martin's axiom
0 references
forcing
0 references
analytic sets
0 references
Polish spaces
0 references
constructibility
0 references
co-analytic sets
0 references
absoluteness
0 references