符号图的特征多项式系数定理及其应用

将简单图的邻接矩阵的特征多项式系数定理推广到适合符号图的情形，并将其用于研究n阶单圈符号图的零度。当$ngeq 5$时，得到了它的上界为n-4，并刻画了零度为n-4的图；得到了单圈符号图的零指数集合．

The Coefficients Theorem of Signed Graph and Its Application

The nullity of a graph is the multiplicity of the eigenvalue zero in its spectrum. The classic coefficients theorem of simple graph is generalized to the case of signed graph. With the help of this theorem, the nullity of signed graph is studied. The upper bound of the nullity of $n(ngeq 5)$-vertex unicyclic signed graphs is shown to be $n-4$. The unicyclic signed graphs with nullity equal to n-2(n-3 or n-4, respectively) are charaterized. Moreover, the nullity set is concerned.