Bipartite biregular Moore graphs

A bipartite graph G=(V,E) with V=V1 U V2 is biregular if all the vertices of a stable set Vi have the same degree ri for i=1,2. In this paper, we give an improved new Moore bound for an infinite family of such graphs with odd diameter. This problem was introduced in 1983 by Yebra, Fiol, and Fàbrega....

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Detalles Bibliográficos
Autores: Araujo Pardo, Martha Gabriela, Dalfó, Cristina, Fiol Mora, Miguel Ángel, López Lorenzo, Ignacio
Tipo de recurso: artículo
Estado:Versión publicada
Fecha de publicación:2021
País:España
Institución:Varias* (Consorci de Biblioteques Universitáries de Catalunya, Centre de Serveis Científics i Acadèmics de Catalunya)
Repositorio:Recercat. Dipósit de la Recerca de Catalunya
OAI Identifier:oai:recercat.cat:10459.1/72274
Acceso en línea:https://doi.org/10.1016/j.disc.2021.112582
http://hdl.handle.net/10459.1/72274
Access Level:acceso abierto
Palabra clave:Bipartite biregular graphs
Moore bound
Diameter
Adjacency spectrum
Descripción
Sumario:A bipartite graph G=(V,E) with V=V1 U V2 is biregular if all the vertices of a stable set Vi have the same degree ri for i=1,2. In this paper, we give an improved new Moore bound for an infinite family of such graphs with odd diameter. This problem was introduced in 1983 by Yebra, Fiol, and Fàbrega. Besides, we propose some constructions of bipartite biregular graphs with diameter d and large number of vertices N(r1,r2;d), together with their spectra. In some cases of diameters d=3, 4, and 5, the new graphs attaining the Moore bound are unique up to isomorphism.