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arXiv 2012.12694math.COmath.SP
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正交对称矩阵与图的并

Orthogonal symmetric matrices and joins of graphs

Rupert H. Levene, Polona Oblak, Helena Šmigoc

摘要:

我们引入了多重矩阵相容性的概念。这给出了两个(可能不连通的)图$G$和$H$的连接成为正交对称矩阵的模式的必要条件,或者等价地,$G\vee H$的不同特征值$q$的最小数目等于2。在附加的假设下,我们证明了这个必要条件也是充分的。作为一个应用,我们证明了当$G$和$H$是完全图的并时,$q(G\vee H)$是2或3,并对每种情况的出现进行了证明.

英文摘要:

We introduce a notion of compatibility for multiplicity matrices. This gives rise to a necessary condition for the join of two (possibly disconnected) graphs $G$ and $H$ to be the pattern of an orthogonal symmetric matrix, or equivalently, for the minimum number of distinct eigenvalues $q$ of $G\vee H$ to be equal to two. Under additional hypotheses, we show that this necessary condition is also sufficient. As an application, we prove that $q(G\vee H)$ is either two or three when $G$ and $H$ are unions of complete graphs, and we characterise when each case occurs.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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