A nearly sign-nonsingular (NSNS) matrix is a real n x n matrix having at least two nonzero terms in the expansion of its determinant with precisely one of these terms having opposite sign to all the other terms. Using graph-theoretic techniques, we study the spectra of irreducible NSNS matrices in normal form. Specifically, we show that such a matrix can have at most one nonnegative eigenvalue, and can have no nonreal eigenvalue z in the sector (z:rg z less than or equal to pi/(n -1)). We also derive results concerning the sign pattern of inverses of these matrices. (C) Elsevier Science Inc., 1996 [References: 9]
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机译：近似符号非奇异（NSNS）矩阵是一个实数n x n矩阵，在其行列式扩展中至少具有两个非零项，而这些项中的一个恰好具有与所有其他项相反的符号。使用图论技术，我们研究了正常形式的不可约NSNS矩阵的光谱。具体而言，我们证明了这样的矩阵最多可以具有一个非负特征值，并且在该扇区中可以不具有非真实特征值z（z： arg z 小于或等于pi /（n -1））。我们还得出有关这些矩阵逆的符号模式的结果。 （C）Elsevier Science Inc.，1996年[参考文献：9]
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