The complete-intersection conjecture for t-intersecting spanning trees

Let Fn,F_{n,\ell} be a spanning forest on nn vertices with \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.

Sources & referencesView supporting material

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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