The highly vertically connected matroid minor conjecture

Let MM be a matroid. For an integer kk, MM is vertically kk-connected if, for every AE(M)A\subseteq E(M) with λM(A)<k1\lambda_M(A)<k-1, either AA or E(M)AE(M)-A is spanning in MM. Write M(Kn)M(K_n) for the cycle matroid of the complete graph, B(Kn)B(K_n) for its bicircular matroid, Un,2nU_{n,2n} for the uniform matroid, and MM^* for the dual matroid. Highly vertically connected matroid minor conjecture. For all n2n\geq 2 there is an integer kk such that, if MM is a vertically kk-connected matroid with M2k|M|\geq 2k, then MM or MM^* has a minor isomorphic to one of M(Kn)M(K_n), B(Kn)B(K_n), or Un,2nU_{n,2n}. The conjecture predicts the unavoidable minors for highly vertically connected matroids in minor-closed classes omitting a uniform matroid; the dual outcomes reflect that the relevant graph and bicircular matroid duals can have highly vertically connected minors.

Sources & referencesView supporting material

Primary source

Jim Geelen and Peter Nelson, “The structure of matroids with a spanning clique or projective geometry”, arXiv:1602.05132 (2016).

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