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For every let be a bounded set with outer measure .
Must there exist an infinite independent set, that is, some infinite such that for all ?
If the sets are closed and have measure , then must there exist an independent set of size ?
Source: erdosproblems.com/501
An accepted solution exists. Settled in another form, for example when its parts resolve differently or the question is open-ended.
The site labels the problem NOT DISPROVABLE, a label which composes
the two questions' outcomes by the catalog's rule (the strongest status holding
of every part). The two questions have different outcomes. Second question:
proved, by Newelski–Pawlikowski–Seredyński 1987, Corollary (1): closed sets of
measure admit an infinite independent set, hence one of size
(refereed). First question: independent of ZFC relative to
. The negative answer holds under CH, by the
countable, null, bounded construction the site attributes to Hechler [He72],
written out in both 2026 notes, and CH holds in Gödel's constructible universe,
so ZFC does not prove the positive answer if ZFC is consistent (the not-provable
side). The positive answer holds after adding random reals to any
model of CH (E. Glazer, draft rev10 of 2026-08-16, self-published, Theorem 1.1
and Corollary 1.2 [Gla26]), so ZFC does not refute it if ZFC is consistent (the
not-disprovable side); earlier, S. Lee proved the positive answer from a full
extension of Lebesgue measure [Lee26], which gives independence relative to a
measurable cardinal. The reviewed evidence supporting Glazer's accepted claim is
the erdosproblems.com editorial adoption of 2026-09-03, which credits Glazer
with the independence; the community database change merged 2026-09-18
(teorth/erdosproblems pull request #400, with the maintainers' recorded
reasoning) is its context. Neither 2026 result is refereed. The author's public
Lean 4 development (github.com/elliotglazer/erdos501) is an unaudited
formalization, a link on the claim pages and not acceptance evidence. Taken as
the status of the conjunction, the exact statement would be independent (the
conjunction is ZFC-equivalent to the first question). The frontmatter lists the
two questions as the problem's parts, and each is settled by an accepted claim
page recording the result and its acceptance evidence:
Glazer's claim settles
the first question (independent) and
the Newelski–Pawlikowski–Seredyński claim
the second (proved);
Hechler's claim settles
the first question's not-provable side, which Glazer's claim also carries, and
Lee's conditional claim
settles neither question alone. The standing in the frontmatter derives from
them: solved, with the claim value answered, the schema's value when the
accepted parts have different outcomes. It departs from NOT DISPROVABLE because
the corpus records each question's settled outcome as a part, where the site's
label composes the two outcomes into the strongest status that holds of both.