Browsing Articles publicats (Matemàtica) by Subject "Moore bound"

Now showing items 1-7 of 7

    • An improved Moore bound and some new optimal families of mixed Abelian Cayley graphs 

      Dalfó, Cristina; Fiol, Miguel Angel; López Lorenzo, Ignacio; Ryan, Joe (Elsevier, 2020)
      We consider the case in which mixed graphs (with both directed and undirected edges) are Cayley graphs of Abelian groups. In this case, some Moore bounds were derived for the maximum number of vertices that such graphs can ...

    • An improved upper bound for the order of mixed graphs 

      Dalfó, Cristina; Fiol, Miguel Angel; López Lorenzo, Ignacio (Elsevier B.V., 2018)
      A mixed graph G can contain both (undirected) edges and arcs (directed edges). Here we derive an improved Moore-like bound for the maximum number of vertices of a mixed graph with diameter at least three. Moreover, a ...

    • Bipartite biregular Moore graphs 

      Araujo Pardo, Martha Gabriela; Dalfó, Cristina; Fiol, Miguel Angel; López Lorenzo, Ignacio (Elsevier, 2021)
      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 ...

    • Degree/diameter problem for mixed graphs 

      López Lorenzo, Ignacio; Pérez Rosés, Hebert (Elsevier, 2015)
      The Degree/diameter problem asks for the largest graphs given diameter and maximum degree. This problem has been extensively studied both for directed and undirected graphs, ando also for special classes of graphs. In this ...

    • New Moore-Like Bounds and Some Optimal Families of Abelian Cayley Mixed Graphs 

      Dalfó, Cristina; Fiol, Miguel Angel; López Lorenzo, Ignacio (2020-06-06)
      Mixed graphs can be seen as digraphs that have both arcs and edges (or digons, that is, two opposite arcs). In this paper, we consider the case where such graphs are Cayley graphs of abelian groups. Such groups can be ...

    • On bipartite-mixed graphs 

      Dalfó, Cristina; Fiol, Miguel Angel; López Lorenzo, Ignacio (Wiley, 2018-04-04)
      Mixed graphs can be seen as digraphs that have both arcs and edges (or digons, that is, two opposite arcs). In this arti- cle, we consider the case where such graphs are bipartite. As main results, we show that in this ...

    • Properties of mixed Moore graphs of directed degree one 

      López Lorenzo, Ignacio; Pujolàs Boix, Jordi (Elsevier, 2015-04-01)
      Mixed graphs of order n such that for any pair of vertices there is a unique trail of length at most k between them are known as mixed Moore graphs. These extremal graphs may only exist for diameter k = 2 and certain ...