A graph is vertex-critical (edge-critical) if deleting any vertex (edge) increases its diameter. A conjecture of Simon and Murty stated thatèvery edge-critical graph of diameter two on vertices contains at most 1 4 2 edges'. This conjecture has been established for suuciently large. For vertex-critical graphs, little is known about the number of edges. Plesn ik implicitly asked whether it is al...

The first 2 PARI-GP files below give the sets of vertices and edges of the Voronoi graph first in dimensions 2 to 6, then in dimension 7. The numerical data are extracted from Jaquet’s thesis [Ja]. The third file, based on Chapters 9 and 14 of [Mar], is devoted to minimal classes in dimensions 2 to 4. We present below a short account of Voronoi’s theory and minimal classes. 1. The perfection ra...

Some properties of minimal open sets and maximal open sets are studied in [1, 2]. In this paper, we define dual concepts of them, namely, maximal closed set and minimal closed set. These four types of subsets appear in finite spaces, for example. More generally, minimal open sets and maximal closed sets appear in locally finite spaces such as the digital line. Minimal closed sets and maximal op...

Let G be a simple connected complex Lie group. The additive eigencone $$ \overline{\Gamma} n(G) is polyhedral cone containing the set of solutions to eigenvalue problem, generalization Hermitian problem. functorial, and for certain subgroups satisfies stronger functoriality property: subgroup determined by inequalities larger eigencone. Belkale Kumar first studied this property invariant under ...