Document Type
Article
Department/Program
Mathematics
Journal Title
Special Matrices
Pub Date
2016
Volume
4
Issue
1
First Page
67
Abstract
A copositive matrix A is said to be exceptional if it is not the sum of a positive semidefinite matrix and a nonnegative matrix. We show that with certain assumptions on A(-1), especially on the diagonal entries, we can guarantee that a copositive matrix A is exceptional. We also show that the only 5-by-5 exceptional matrix with a hollow nonnegative inverse is the Horn matrix (up to positive diagonal congruence and permutation similarity).
Recommended Citation
Johnson, C. R., & Reams, R. B. (2016). Sufficient conditions to be exceptional. Special Matrices, 4(1).
DOI
10.1515/spma-2016-0007
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