Optimal list threshold for majority edge-colourings

Prove that every graph with minimum degree at least k^2 admits a 1/k-majority edge colouring from every assignment of lists of size k+1, for every integer k≥2.

Background

The paper proves a list-colouring result with minimum-degree threshold 2k2−2k and observes that the threshold can be lowered to approximately k2−k for certain regular graphs. This motivates a direct strengthening of the non-list conjecture to arbitrary list assignments.

The proposed statement would determine the optimal order and, up to the known obstruction at degree k2−1, the exact threshold for 1/k-majority edge colourings from lists of size k+1.

References

This observation supports a direct strengthening of Conjecture 5 towards the list setting, which we dare to pose below.

Conjecture 22. For every integer k ≥ 2, if a graph G has minimum degree 8(G) > k2, then G has a 1/k-majority edge colouring from any lists of size k + 1.

On list extensions of the majority edge colourings  (2502.12688 - Pękała et al., 18 Feb 2025) in Conjecture 22, Section 7 (Concluding remarks)