The complete-intersection conjecture for t-intersecting spanning trees

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Let Fn,ℓF_{n,\ell} be a spanning forest on nn vertices with ℓ\ell edges, whose components have either kk or k+1k+1 vertices, with component sizes as equal as possible. Let Fn,t,j\mathcal{F}_{n,t,j} be the family of all spanning trees that contain at least t+jt+j of the t+2jt+2j edges of Fn,t+2jF_{n,t+2j}. A family of spanning trees is tt-intersecting if any two trees in it have at least tt edges in common.

Complete-intersection conjecture. For any tt and nn, there exists a jj such that Fn,t,j\mathcal{F}_{n,t,j} is the largest tt-intersecting set of spanning trees.

This conjecture is presented as a “Complete Intersection Theorem”-type statement, extending the comparison between fixed-edge constructions and families requiring many edges from a balanced spanning forest. The supplied status evidence says that the conjecture has since been proved by Elizaveta Iarovikova and Andrey Kupavskii.

References

Primary source

Peter Frankl, Glenn Hurlbert, Ferdinand Ihringer, Andrey Kupavskii, Nathan Lindzey, Karen Meagher and Venkata Raghu Tej Pantangi, “Intersecting Families of Spanning Trees”, arXiv:2502.08128 (2025).

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