Morris's conjecture on regular generators of non-FC families

About 9 years old · traced to

Let [n]={1,…,n}[n]=\{1,\ldots,n\} and let U(S)U(\mathcal{S}) denote the union of the sets in S\mathcal{S}. A minimal generator of a union-closed family F\mathcal{F} is a family whose generated union-closed family is F\mathcal{F} and which is minimal with this property. A union-closed family is Non-FC if it does not satisfy Frankl's conjecture. A generator S\mathcal{S} is regular when, for every nonempty A∈SA\in\mathcal{S} and every i∈[n]i\in[n], replacing AA by A∪{i}A\cup\{i\} still generates a Non-FC union-closed family. Morris's conjecture. If U(S)=[n]U(\mathcal{S})=[n] for n≥3n\geq 3, and S\mathcal{S} is a minimal generator for a Non-FC union-closed family F\mathcal{F}, then S\mathcal{S} is regular. The paper states that it constructs a counterexample to this conjecture, so the claim is refuted.

References

Primary source

Jonad Pulaj, “Cutting Planes for Families Implying Frankl's Conjecture”, arXiv:1702.05947 (2018).

Progress summary

Refreshed
Claimed solved

A 2017 paper says it found a counterexample to Morris's conjecture, but the retrieved evidence does not independently verify the claim.

Morris's 2006 conjecture concerns whether every minimal generator of a non-Frankl union-closed family is regular when its union is [n][n] for n≥3n\ge 3.

February 2017 counterexample claim

The paper Cutting Planes for Families Implying Frankl's Conjecture reports constructing a counterexample to Morris's conjecture, which would refute it. The retrieved record does not provide independent verification of that construction.

Current status (as of September 2026): A counterexample is claimed in the 2017 paper, but the retrieved sources do not establish that the construction has been independently verified.

Sources

Solutions 0

No solutions have been posted yet.