Large-girth minor conjecture for arbitrary cosimple matroids

From papers

Let U2,qU_{2,q} be the qq-element rank-22 uniform matroid, and more generally let Ut,qU_{t,q} be the qq-element rank-tt uniform matroid. Let M(Kt)M(K_t) be the graphic matroid of the complete graph KtK_t, and let M(Kt)M(K_t)^* be its dual. Large-girth minor conjecture. For every positive integer tt, there exists an integer p(t)p(t) such that every cosimple matroid with girth at least p(t)p(t) contains at least one of

U2,t+2,Ut,t+2,M(Kt),M(Kt)U_{2,t+2},\quad U_{t,t+2},\quad M(K_t),\quad M(K_t)^*

as a minor.

The conjecture seeks a finite list of unavoidable minors for arbitrary cosimple matroids of sufficiently large girth, extending the representable case. The source presents it as a natural conjecture, with no resolution supplied.

Progress summary

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Sources & referencesView supporting material

Primary source

James Davies, Meike Hatzel, Kolja Knauer, Rose McCarty and Torsten Ueckerdt, “Girth in GF(q)-representable matroids”, arXiv:2504.21797 (2025).

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