Abstract
We investigate the solution set of the following matrix equation: A T B = J +diag(d), where A and B are n × n {0, 1} 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 A d −1 and B d −1 have full supports, where d −1 = (d −11 , ..., d −1n )T; both A and B have constant column sums; d −1 · 1 ≠ −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 (α,ω)-graphs. We also deduce consequences for “minimal” polyhedra with {0, 1} vertices having non-{0, 1} constraints, and “minimal” polyhedra with {0, 1} constraints having non-{0, 1} vertices.
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Gasparyan, G. (1998). Bipartite Designs. In: Bixby, R.E., Boyd, E.A., Ríos-Mercado, R.Z. (eds) Integer Programming and Combinatorial Optimization. IPCO 1998. Lecture Notes in Computer Science, vol 1412. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-69346-7_3
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DOI: https://doi.org/10.1007/3-540-69346-7_3
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