김동규

Bouchet (1987) defined delta-matroids by relaxing the base exchange axiom of matroids. Oum (2009) introduced a graphic delta-matroid from a pair of a graph and its vertex subset. We define a $\mathrm{\Gamma }$-graphic delta-matroid for an abelian group $\mathrm{\Gamma }$, which generalizes a graphic delta-matroid. For an abelian group $\mathrm{\Gamma }$, a $\mathrm{\Gamma }$-labelled graph is a graph whose …

Tutte (1961) proved that every simple $3$-connected graph $G$ has an edge $e$ such that $G\setminus e$ or $G/e$ is simple $3$-connected, unless $G$ is isomorphic to a wheel. We call such an edge non-essential. Oxley and Wu (2000) proved that every simple $3$-connected graph has at least $2$ non-essential edges unless …

Even delta-matroids generalize matroids, as they are defined by a certain basis exchange axiom weaker than that of matroids. One natural example of even delta-matroids comes from a skew-symmetric matrix over a given field $K$, and we say such an even delta-matroid is representable over the field $K$. Interestingly, a matroid is representable over $K$ …