Minimum rank and maximum eigenvalue multiplicity of symmetric tree sign patterns

Date
2006-10-01
Authors
DeAlba, Luz
Hardy, Timothy
Hentzel, Irvin
Hogben, Leslie
Wangsness, Amy
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Altmetrics
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Mathematics
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Abstract

The set of real matrices described by a sign pattern (a matrix whose entries are elements of {+, −, 0}) has been studied extensively but only loose bounds were available for the minimum rank of a tree sign pattern. A simple graph has been associated with the set of symmetric matrices having a zero–nonzero pattern of off-diagonal entries described by the graph, and the minimum rank/maximum eigenvalue multiplicity among matrices in this set is readily computable for a tree. In this paper, we extend techniques for trees to tree sign patterns and trees allowing loops (with the presence or absence of loops describing the zero–nonzero pattern of the diagonal), allowing precise computation of the minimum rank of a tree sign pattern and a tree allowing loops. For a symmetric tree sign pattern or a tree that allows loops, we provide an algorithm that allows exact computation of maximum multiplicity and minimum rank, and can be used to obtain a symmetric integer matrix realizing minimum rank.

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This is a manuscript of an article from Linear Algebra and its Applications 418 (2006): 394, doi:10.1016/j.laa.2006.02.018. Posted with permission.

Keywords
Sign pattern matrix, Symmetric tree sign pattern, Minimum rank, Maximum multiplicity, Tree, Graph
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