COMBINATORICS
2006
13 years 11 months ago
2006
COMBINATORICS
2006
13 years 11 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 11 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 11 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 11 months ago
2006
COMBINATORICS
2006
13 years 11 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 11 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 11 months ago
2006
Let Sm,n be the graph on the vertex set Zm
COMBINATORICS
2006
13 years 11 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 11 months ago
2006