Research notes on every problem, and a library of the papers behind them. Built from the open erdos repository.
Updated
Claim. Let be cardinals. A family of analytic functions taking at most distinct values at every point has at most members. This is the remark after the theorem in P. Erdős, An interpolation problem associated with the continuum hypothesis, Michigan Math. J. 11 (1964), 9--10 (p. 10), proved by the theorem's counting argument. Two distinct entire functions agree on a countable set, so in a subfamily of functions fewer than points carry a coincidence, and at any other point the subfamily takes distinct values. For Problem 1119, with the problem's in the role of , the answer is yes in ZFC for every with .
Covers. Every cardinal of the problem with . The remaining case is undecidable by Kumar and Shelah's model and Schilhan and Weinert's result. Hayman's 1974 list calls the case easy to see, which is how the site's commentary records it.
Depends on. No page of this wiki.
Acceptance. Refereed: the result appears in a journal paper in the Michigan Mathematical Journal.
Formalization. The formalization link is Boris Alexeev's lean-proofs file
src/latest/ErdosProblems/Erdos1119.lean, at the revision that
formal-conjectures names as the formal proof of erdos_1119.variants.easy_case.
Its header calls it a formalization of a solution to the problem and names Paul
Erdős as the informal author and Codex and GPT-5.6 Sol as the formal authors. It
proves erdos_1119.variants.easy_case and Erdős's countable theorem. The corpus
has not built it, so no formalized evidence is listed. A separate Lean package
by Collin Yuanjie Ren, noted in the community database, formalizes Erdős's
countable-values theorem in both directions. The problem asks only about
, so that package is not a claim about it.