Enviaments recents

  • Some spectral and quasi-spectral characterizations of distance-regular graphs 

    Abiad, Aida; Van Dam, Edwin R; Fiol Mora, Miquel Àngel (2016-10-01)
    Article
    Accés restringit per política de l'editorial
    In this paper we consider the concept of preintersection numbers of a graph. These numbers are determined by the spectrum of the adjacency matrix of the graph, and generalize the intersection numbers of a distance-regular ...
  • The spectral excess theorem for distance-regular graphs having distance-d graph with fewer distinct eigenvalues 

    Fiol Mora, Miquel Àngel (2016-06-01)
    Article
    Accés restringit per política de l'editorial
    Let Gamma be a distance-regular graph with diameter d and Kneser graph K = Gamma(d), the distance-d graph of Gamma. We say that Gamma is partially antipodal when K has fewer distinct eigenvalues than Gamma. In particular, ...
  • Symmetry breaking in tournaments 

    Lozano Bojados, Antoni (2013-03-24)
    Article
    Accés obert
    We provide upper bounds for the determining number and the metric dimension of tournaments. A set of vertices S in V(T) is a determining set for a tournament T if every nontrivial automorphism of T moves at least one vertex ...
  • Abelian Cayley digraphs with asymptotically large order for any given degree 

    Aguiló Gost, Francisco de Asis L.; Fiol Mora, Miquel Àngel; Pérez Mansilla, Sonia (2016-04-29)
    Article
    Accés obert
    Abelian Cayley digraphs can be constructed by using a generalization to Z(n) of the concept of congruence in Z. Here we use this approach to present a family of such digraphs, which, for every fixed value of the degree, ...
  • Sequence mixed graphs 

    Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; López, Nacho (2016-12)
    Article
    Accés obert
    A mixed graph can be seen as a type of digraph containing some edges (or two opposite arcs). Here we introduce the concept of sequence mixed graphs, which is a generalization of both sequence graphs and literated line ...
  • Algorithmic recognition of infinite cyclic extensions 

    Cavallo, Bren; Delgado Rodríguez, Jordi; Kahrobaei, Delaram; Ventura Capell, Enric (2016-10-25)
    Article
    Accés restringit per política de l'editorial
    We prove that one cannot algorithmically decide whether a finitely presented Z-extension admits a finitely generated base group, and we use this fact to prove the undecidability of the BNS invariant. Furthermore, we show ...
  • Distance mean-regular graphs 

    Fiol Mora, Miquel Àngel; Diego, Victor (2016)
    Article
    Accés restringit per política de l'editorial
    We introduce the concept of distance mean-regular graph, which can be seen as a generalization of both vertex-transitive and distance-regular graphs. Let G be a graph with vertex set V , diameter D, adjacency matrix A, and ...
  • José Gómez Martí 1968-2014: in memoriam 

    Fiol Mora, Miquel Àngel (Societat Catalana de Matemàtiques (SCM), 2015)
    Article
    Accés obert
  • A note on the order of iterated line digraphs 

    Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel (Wiley, 2016-07-27)
    Article
    Accés restringit per política de l'editorial
    Given a digraph G, we propose a new method to find the recurrence equation for the number of vertices n_k of the k-iterated line digraph L_k(G), for k>= 0, where L_0(G) = G. We obtain this result by using the minimal polynomial ...
  • Deterministic hierarchical networks 

    Barrière Figueroa, Eulalia; Comellas Padró, Francesc de Paula; Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel (2016)
    Article
    Accés restringit per política de l'editorial
    It has been shown that many networks associated with complex systems are small-world (they have both a large local clustering coefficient and a small diameter) and also scale-free (the degrees are distributed according ...

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