Bipartite Designs
نویسنده
چکیده
We investigate the solution set of the following matrix equation: A T B = J + diag(d); where A and B are n n f0; 1g matrices, J is the matrix with all entries equal one and d is a full support vector. We prove that in some special cases (such as: both Ad ?1 and Bd ?1 have full supports, where d ?1 = (d ?1 1 ; : : : ; d ?1 n) T ; both A and B have constant column sums; d ?1 1 6 = ?1; and A has constant row sum etc.) these solutions have strong structural properties. We show how the results relate to design theory, and then apply the results to derive sharper characterizations of (; !)-graphs. We also deduce consequences for both polyhedra with f0; 1g vertices and not necessary with f0; 1g constraints, and polyhedra with f0; 1g constraints and not necessary with f0; 1g vertices.
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تاریخ انتشار 1998