The graphs for which the maximum multiplicity of an eigenvalue is two
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چکیده
منابع مشابه
The Graphs for which the Maximum Multiplicity of an Eigenvalue is Two
Characterized are all simple undirected graphs G such that any real symmetric matrix that has graph G has no eigenvalues of multiplicity more than 2. All such graphs are partial 2-trees (and this follows from a result for rather general fields), but only certain partial 2-trees guarantee maximum multiplicity 2. Among partial linear 2-trees, they are only those whose vertices can be covered by t...
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15 صفحه اولGraphs for which the least eigenvalue is minimal, II
We continue our investigation of graphsG for which the least eigenvalue λ(G) is minimal among the connected graphs of prescribed order and size. We provide structural details of the bipartite graphs that arise, and study the behaviour of λ(G) as the size increases while the order remains constant. The non-bipartite graphs that arise were investigated in a previous paper [F.K. Bell, D. Cvetković...
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Let G be a connected graph whose least eigenvalue λ(G) is minimal among the connected graphs of prescribed order and size. We show first that either G is complete or λ(G) is a simple eigenvalue. In the latter case, the sign pattern of a corresponding eigenvector determines a partition of the vertex set, and we study the structure of G in terms of this partition. We find that G is either biparti...
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ژورنال
عنوان ژورنال: Linear and Multilinear Algebra
سال: 2009
ISSN: 0308-1087,1563-5139
DOI: 10.1080/01445340802354580