We consider the question of characterizing Pfaffian graphs. We exhibit an infinite family of non-Pfaffian graphs minimal with respect to the matching minor relation. This is in sha...
The unfolding of a system represents in a single branching structure all its possible computations: it is the cornerstone both of semantical constructions and of efficient partial ...
Let be a triangle-free distance-regular graph with diameter d 3, valency k 3 and intersection number a2 = 0. Assume has an eigenvalue with multiplicity k. We show that if for ...
Algorithms are given for computing the number of n-element diagonal sets and the number of n-element strongly diagonal sets of binary sequences of length at most 2n - 2. The first...
Robertson and Seymour (1990) proved that graphs of bounded tree-width are well-quasi-ordered by the graph minor relation. By extending their arguments, Geelen, Gerards, and Whittle...