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Three-connected graphs whose maximum nullity is at most three. (English) Zbl 1145.05037

Let \(G=(V,E)\) be a graph with \(V=\{1,2,\dots,n\}\). Define \(\mathcal S(G)\) as the set of all \(n\times n\) real-valued symmetric matrices \(A=[a_{i,j}]\) with \(a_{i,j}\neq 0\), \(i\neq j\), if and only if \(ij\in E\). The maximum nullity of \(G\), denoted by \(M(G)\), is the largest possible nullity of any matrix \(A\in\mathcal S(G)\). If we denote by \(mr(G)\) the smallest possible rank of any matrix \(A\in\mathcal S(G)\), then \(M(G)+mr(G)=n\). In this paper it is proved that \(k\)-connected graphs \(G\) have \(M(G)\geq k\) and that \(k\)-connected partial \(k\)-paths \(G\) have \(M(G)=k\). For \(3\)-connected graphs \(M(G)=3\) if and only if \(G\) is a partial \(3\)-path.

MSC:

05C50 Graphs and linear algebra (matrices, eigenvalues, etc.)
15A03 Vector spaces, linear dependence, rank, lineability
05C83 Graph minors
Full Text: DOI

References:

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