Intertwining Connectivities in Representable Matroids
Tony Huynh, Stefan van Zwam · SIAM Journal on Discrete Mathematics · 2014
Let $M$ be a representable matroid and $Q, R, S, T$ subsets of the ground set such that the smallest separation that separates $Q$ from $R$ has order $k$, and the smallest separation that separates $S$ from $T$ has order $l$. We prove that if $M$ is sufficiently large, then there is an element $e$ such that in one of $M\backslash e$ and $M\!/e$ both connectivities are preserved. For matroids representable over a finite field we prove a stronger result: we show that we can remove $e$ such that both a connectivity and a minor of $M$ are preserved. (A corrected version is attached.)