3 problems

Let $M$ be a matroid with ground set $E$. For $k\in\mathbb{N}$, let $\psi_i\colon E\to\Gamma_i$ be group labelings into abelian groups $\Gamma_i$, let $f_i\in\Gamma_i$ be forbidden…

Schrijver–Seymour's conjecture.

Let $M$ be a matroid, $psi\colon E \to \Gamma$ a labeling from the ground set $E$ of $M$ to an abelian group $\Gamma$, and $F \subseteq \Gamma$ a finite collection of forbidden lab…