Title:
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Limit points of eigenvalues of (di)graphs (English) |
Author:
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Zhang, Fuji |
Author:
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Chen, Zhibo |
Language:
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English |
Journal:
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Czechoslovak Mathematical Journal |
ISSN:
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0011-4642 (print) |
ISSN:
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1572-9141 (online) |
Volume:
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56 |
Issue:
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3 |
Year:
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2006 |
Pages:
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895-902 |
Summary lang:
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English |
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Category:
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math |
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Summary:
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The study on limit points of eigenvalues of undirected graphs was initiated by A. J. Hoffman in 1972. Now we extend the study to digraphs. We prove: 1. Every real number is a limit point of eigenvalues of graphs. Every complex number is a limit point of eigenvalues of digraphs. 2. For a digraph $D$, the set of limit points of eigenvalues of iterated subdivision digraphs of $D$ is the unit circle in the complex plane if and only if $D$ has a directed cycle. 3. Every limit point of eigenvalues of a set $\mathcal {D}$ of digraphs (graphs) is a limit point of eigenvalues of a set $\ddot{\mathcal {D}}$ of bipartite digraphs (graphs), where $\ddot{\mathcal {D}}$ consists of the double covers of the members in $\mathcal {D}$. 4. Every limit point of eigenvalues of a set $\mathcal {D}$ of digraphs is a limit point of eigenvalues of line digraphs of the digraphs in $\mathcal {D}$. 5. If $M$ is a limit point of the largest eigenvalues of graphs, then $-M$ is a limit point of the smallest eigenvalues of graphs. (English) |
Keyword:
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limit point |
Keyword:
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eigenvalue of digraph (graph) |
Keyword:
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double cover |
Keyword:
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subdivision digraph |
Keyword:
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line digraph |
MSC:
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05C50 |
MSC:
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15A48 |
idZBL:
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Zbl 1164.05412 |
idMR:
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MR2261661 |
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Date available:
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2009-09-24T11:39:13Z |
Last updated:
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2020-07-03 |
Stable URL:
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http://hdl.handle.net/10338.dmlcz/128114 |
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Reference:
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