COMBINATORICS
2006
13 years 4 months ago
2006
COMBINATORICS
2006
13 years 4 months ago
2006
We investigate the existence of edge-magic labellings of countably infinite graphs by abelian groups. We show for that for a large class of abelian groups, including the integers ...
COMBINATORICS
2006
13 years 4 months ago
2006
We give a new derivation of the threshold of appearance of the k-core of a random graph. Our method uses a hybrid model obtained from a simple model of random graphs based on rand...
COMBINATORICS
2006
13 years 4 months ago
2006
We show how to construct a cubic partial cube from any simplicial arrangement of lines or pseudolines in the projective plane. As a consequence, we find nine new infinite families...
COMBINATORICS
2006
13 years 4 months ago
2006
COMBINATORICS
2006
13 years 4 months ago
2006
The natural forms of the Leibniz rule for the kth derivative of a product and of Fa`a di Bruno's formula for the kth derivative of a composition involve the differential oper...
COMBINATORICS
2006
13 years 4 months ago
2006
We prove that n+h 4 vertex guards are always sufficient to see the entire interior of an n-vertex orthogonal polygon P with an arbitrary number h of holes provided that there exis...
COMBINATORICS
2006
13 years 4 months ago
2006
Let Sm,n be the graph on the vertex set Zm
COMBINATORICS
2006
13 years 4 months ago
2006
The group PGL(2, q), q = pn, p an odd prime, is 3-transitive on the projective line and therefore it can be used to construct 3-designs. In this paper, we determine the sizes of o...
COMBINATORICS
2006
13 years 4 months ago
2006