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Erdős Problem #1044

SOLVED LEANdatabase updated 2026-04-28

Resolved in some way other than a straight proof or disproof — usual for open-ended questions, or for multi-part problems whose parts went different ways. A solution has also been checked by machine, in Lean.

What the community database records, not our verdict. erdosproblems.com no longer shows statuses (why).

The polynomials under consideration: those of the form \(f(z)=\prod_{i=1}^n(z-z_i)\), for some \(n\geq 1\), where \(\lvert z_i\rvert\leq 1\) for all \(i\).

\(\Lambda(f)\), the maximum of the lengths of the boundaries of the connected components of \(\{ z: \lvert f(z)\rvert<1\}\), where the length of a subset of \(\mathbb{C}\) is its \(1\)-dimensional Hausdorff measure.

Let \(f(z)=\prod_{i=1}^n(z-z_i)\in\mathbb{C}[x]\) where \(\lvert z_i\rvert\leq 1\) for all \(i\). If \(\Lambda(f)\) is the maximum of the lengths of the boundaries of the connected components of \[ \{ z: \lvert f(z)\rvert<1\} \] then determine the infimum of \(\Lambda(f)\). A problem of Erdős, Herzog, and Piranian [EHP58]. This has been resolved by Tang, who proved that the infimum of \(\Lambda(f)\) over all such \(f\) is \(2\).
Statement as formalized in Formal Conjectures (Google DeepMind, Apache-2.0) · their label: research solved · 3 further variants / known partial results in the Lean file. The authoritative wording is on erdosproblems.com/1044.
Prizenone
Topicsanalysis
Statement in LeanFormal Conjectures
Solution in Leanyes
Original pageerdosproblems.com/1044
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