科研之友
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摘要
A P-set of a symmetric matrix A is a set alpha of indices such that the nullity of the matrix obtained from A by removing rows and columns indexed by alpha is vertical bar alpha vertical bar more than the nullity of A. It is known that each subset of a P-set is a P-set. It is also known that a set of indices such that each singleton subset is a P-set need not be a P-set. This note shows that if all pairs of vertices of a set with at least two elements are P-sets, then the set is a P-set.
- 出版日期2015-6-15
