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Let be finite and be an infinite cardinal. Let be cardinals for all .
Is it true that
implies
Here means cardinal addition, so that if is infinite.
Let be finite and be an infinite cardinal. Let and let be cardinals for all .
Is it true that
implies
Here means cardinal addition, so that if is infinite.
Source: erdosproblems.com/1167
No claim settles this problem.
The site's label is OPEN. The corrected Statement, with the conditions and , is open; the counterexample to the site's wording at is credited in the Notes and recorded on a rejected claim page.
The site's wording follows the booklet item [Va99, 7.79] and puts no
condition on or on the , and, read as the site words it,
the implication is false. For and , the premise
says only that , which
holds, while needs a subset of of size
. For , and , the premise
holds: either some -set has color , or all of is
homogeneous in color . The constant coloring of with color
refutes the conclusion. Both failures are boundary cases of a dropped range, and
the change adds the conditions and of the
Erdős–Hajnal list, which exclude them. Komjáth's Problem 2 ([Ko25b], p. 419)
states the question for finite with and a condition on
that the site's curator reads as , taking the printed
inequality for a misprint. The curator's reply in the
discussion thread points to
these conditions rather than accepting a disproof, and the site keeps the label
OPEN. The
formal-conjectures statement file
adds and and proves the first counterexample as
its test lemma erdos_1167.unrestricted_is_false. That lemma is in a statement
file, so it is not a formalization link and gets no claim page, and the corpus
has not built it. Rafik Zeraoulia gave the first counterexample in a note of 31
January 2026. It answers the site's wording, not the corrected Statement, so it
does not count toward the problem's standing; it is credited here and recorded
on
Zeraoulia's rejected claim page (2026).
The problem's standing judges the corrected Statement.