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JCT
2000
14 years 9 months ago
2000
Generalizing the notion of placing rooks on a Ferrers board leads to a new class of combinatorial models and a new class of rook polynomials. Connections are establishedwith absolu...
JCT
2002
14 years 9 months ago
2002
It is proved that there is a function f : N N such that the following holds. Let G be a graph embedded in a surface of Euler genus g with all faces of even size and with edge-wid...
JCT
1998
14 years 9 months ago
1998
We show that any k-regular bipartite graph with 2n vertices has at least ((k−1)k−1 kk−2 )n perfect matchings (1-factors). Equivalently, this is a lower bound on the permanent...
JCT
2010
14 years 8 months ago
2010
A k-signed r-set on [n] = {1, ..., n} is an ordered pair (A, f), where A is an rsubset of [n] and f is a function from A to [k]. Families A1, ..., Ap are said to be cross-intersec...
JCT
2010
14 years 8 months ago
2010
We call a coloring of the edge set of a graph G a b-bounded coloring if no color is used more than b times. We say that a subset of the edges of G is rainbow if each edge is of a ...