The highly vertically connected matroid minor conjecture

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Let MM be a matroid. For an integer kk, MM is vertically kk-connected if, for every A⊆E(M)A\subseteq E(M) with λM(A)<k−1\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 M∗M^* for the dual matroid. Highly vertically connected matroid minor conjecture. For all n≥2n\geq 2 there is an integer kk such that, if MM is a vertically kk-connected matroid with ∣M∣≥2k|M|\geq 2k, then MM or M∗M^* 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.

References

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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