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COMBINATORICS
2004
13 years 9 months ago
2004
The class of square (0, 1, -1)-matrices whose rows are nonzero and mutually orthogonal is studied. This class generalizes the classes of Hadamard and Weighing matrices. We prove t...
COMBINATORICS
2004
13 years 9 months ago
2004
In the 1960's, Tutte presented a decomposition of a 2-connected finite graph into 3-connected graphs, cycles and bonds. This decomposition has been used to reduce problems on...
COMBINATORICS
2004
13 years 9 months ago
2004
Let G be the intersection graph of a finite family of convex sets obtained by translations of a fixed convex set in the plane. We show that every such graph with clique number k i...
COMBINATORICS
2004
13 years 9 months ago
2004
We introduce intersection schemes (a generalization of uniform oriented matroids of rank 3) to describe the combinatorial properties of arrangements of pseudocircles in the plane ...
COMBINATORICS
2004
13 years 9 months ago
2004
We consider Class-Uniformly Resolvable Group Divisible Designs (CURGDD), which are resolvable group divisible designs in which each of the resolution classes has the same number o...