Now showing items 1-8 of 8

  • A family of mixed graphs with large order and diameter 2 

    Araujo Pardo, Gabriela; Balbuena Martínez, Maria Camino Teófila; Miller, Mirka; Zdimalova, Maria (2017-02)
    Article
    Open Access
    A mixed regular graph is a connected simple graph in which each vertex has both a fixed outdegree (the same indegree) and a fixed undirected degree. A mixed regular graphs is said to be optimal if there is not a mixed ...
  • An algebraic approach to lifts of digraphs 

    Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; Miller, Mirka; Ryan, Joe; Siran, Josef (2018-12-07)
    Article
    Open Access
    We study the relationship between two key concepts in the theory of (di)graphs: the quotient digraph, and the lift Ga of a base (voltage) digraph. These techniques contract or expand a given digraph in order to study its ...
  • An overview of the degree/diameter problem for directed, undirected and mixed graphs 

    Miller, Mirka (Iniciativa Digital Politècnica, 2011)
    Conference report
    Open Access
    A well-known fundamental problem in extremal graph theory is the degree/diameter problem, which is to determine the largest (in terms of the number of vertices) graphs or digraphs or mixed graphs of given maximum degree, ...
  • An overview of the Degree/Diameter Problem for directed, undirected and mixed graphs 

    Miller, Mirka (2010-06-11)
    Audiovisual
    Open Access
  • Approximate results for rainbow labelings 

    Lladó Sánchez, Ana M.; Miller, Mirka (2017-03)
    Article
    Open Access
    A simple graph G=(V,E) is said to be antimagic if there exists a bijection f:E¿[1,|E|] such that the sum of the values of f on edges incident to a vertex takes different values on distinct vertices. The graph G is distance ...
  • On quotient digraphs and voltage digraphs 

    Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; Miller, Mirka; Ryan, Joe (2016)
    External research report
    Open Access
    In this note we present a general approach to construct large digraphs from small ones. These are called expanded digraphs, and, as particular cases, we show their close relationship between voltage digraphs and line ...
  • On quotient digraphs and voltage digraphs 

    Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; Miller, Mirka; Ryan, Joe (2017-10)
    Article
    Open Access
    We study the relationship between two key concepts in the theory of digraphs, those of quotient digraphs and voltage digraphs. These techniques contract or expand a given digraph in order to study its characteristics,or ...
  • On the nonexistence of almost Moore digraphs 

    Conde Colom, Josep; Gimbert Quintilla, Joan; González Rovira, Josep; Miller, Mirka; Miret Biosca, Josep Maria (2014-07-01)
    Article
    Restricted access - publisher's policy
    Digraphs of maximum out-degree at most d > 1, diameter at most k > 1 and order N(d, k) = d + ... + d(k) are called almost Moore or (d, k)-digraphs. So far, the problem of their existence has been solved only when d = 2, 3 ...