Determine whether combinatorics distinguish free and nearly free arrangements in the exceptional range
Determine whether there exist a free line arrangement A and a nearly free line arrangement B with the same combinatorics, specifically in the case d1 = m + 1 and 2m + 3 ≤ d, where m denotes the maximal multiplicity and d the number of lines.
References
For instance, the free arrangement A with exponents (m + 1, m + 1) and the nearly free arrangement B with exponents (m, m + 3, m + 3) satisfy τ (A) = τ (B). We do not know whether such a pair of arrangements A, B exists, such that A and B have the same combinatorics.
— On the module of derivations of a line arrangement
(2503.01624 - Dimca, 3 Mar 2025) in Remark 5.4, Section 5, p. 20