Half-factor conjecture for full-domain permutation groups

Prove or refute that every finite permutation group G acting on its full domain Ω satisfies dimN(H_{G,Ω}) ≥ ⌈H(G)/2⌉, where dimN is the Natarajan dimension and H(G) is the permutation-group height.

Background

The paper establishes the inequality when the closure operator induced by pointwise stabilizers is a matroid closure, and shows that the constant 1/2 is sharp for symmetric groups and products such as S_3k. The conjecture concerns arbitrary finite permutation groups acting on the entire underlying set, including groups whose closure operators are not matroidal.

The authors note that commuting stabilizer moves do not suffice in general, so a proof may need to construct Natarajan squares from noncommuting moves. A counterexample would refute the proposed universal lower bound.

References

The following problems are open.

\paragraph{1. The factor one half.} Prove or refute \cref{conj:half}: $\dimN(H{G}{\Omega})\ge\lceilH(G)/2\rceil$ for every finite permutation group acting on its full domain.

— Learning a Group Element from Its Action: Galois Correspondences, Optimal ERM, and an Abel-Ruffini Threshold for the Natarajan Dimension  (2610.18154 - Li, 13 Oct 2026) in Conjecture 1 / Section 4, “The factor one half”; Section 7, Discussion and open problems, paragraph 1