On the spectrum of an extremal graph with four eigenvalues

doi:10.1016/j.disc.2006.05.010

Discrete Mathematics

Volume 306, Issue 18, 28 September 2006, Pages 2241-2244

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Abstract

In this note we study some properties of the spectrum of a connected graph G with four different eigenvalues, and (spectrally maximum) diameter three. When G is regular, this is the case, for instance, when G is a distance-regular graph.

Keywords

Graph

Adjacency matrix

Four eigenvalues

Diameter three

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^☆: Work supported by the Ministry of Science and Technology, Spain, and the European Regional Development Fund (ERDF) under project TIC-2001-2171.

Discrete Mathematics

NoteOn the spectrum of an extremal graph with four eigenvalues☆

Abstract

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Note
On the spectrum of an extremal graph with four eigenvalues☆