EJC
2007
13 years 9 months ago
2007
We give a construction to obtain a t-design from a t-wise balanced design. More precisely, given a positive integer k and a t(v, {k1, k2, . . . , ks}, λ) design D, with with all ...
EJC
2007
13 years 9 months ago
2007
EJC
2007
13 years 9 months ago
2007
We give a characterization of the root shadow spaces of buildings whose types correspond to Dynkin diagrams. The results generalize earlier geometric point-line characterizations ...
EJC
2007
13 years 9 months ago
2007
Abstract. Given a simplicial hyperplane arrangement H and a subspace arrangement A embedded in H, we define a simplicial complex ∆A,H as the subdivision of the link of A induced...
EJC
2007
13 years 9 months ago
2007
Let A and B be hypergraphs with a common vertex set V . In a (p, q, A ∪ B) Bart-Moe game, the players take turns selecting previously unclaimed vertices of V . The game ends whe...
EJC
2007
13 years 9 months ago
2007
It is known that the area of all Catalan paths of length n is equal to 4n − `2n+1 n ´ , which coincides
EJC
2007
13 years 9 months ago
2007
EJC
2007
13 years 9 months ago
2007
We present a new family of locally 5–arc transitive graphs. The graphs constructed are bipartite with valency {2m + 1, 2m}. The actions of the automorphism group on the two bipa...
EJC
2007
13 years 9 months ago
2007
We prove a conjecture of F. Chapoton relating certain enumerative invariants of (a) the cluster complex associated by S. Fomin and A. Zelevinsky with a finite root system and (b)...
EJC
2007
13 years 9 months ago
2007
The cone ˆG of a finite graph G is obtained by adding a new vertex p, called the cone point, and joining each vertex of G to p by a simple edge. We show that the rank of the red...