Recent Submissions

  • Green operators of networks with a new vertex 

    Carmona Mejías, Ángeles; Encinas Bachiller, Andrés Marcos; Gago Álvarez, Silvia; Mitjana Riera, Margarida (Elsevier, 2016-02)
    Article
    Open Access
    Any elliptic operator defines an automorphism on the orthogonal subspace to the eigenfunctions associated with the lowest eigenvalue, whose inverse is the orthogonal Green operator. In this study, we show that elliptic ...
  • Completion and decomposition of hypergraphs into dominating sets of graphs 

    Martí Farré, Jaume; Mora Giné, Mercè; Ruiz Muñoz, José Luis (2015-11)
    Article
    Restricted access - publisher's policy
    The collection of the vertex dominating sets of a graph defines a hypergraph on the set of vertices of the graph. However, there are hypergraphs H that are not the collection of the vertex dominating sets of any graph. ...
  • Connectivity and other invariants of generalized products of graphs 

    López Masip, Susana Clara; Muntaner Batle, Francesc Antoni (2015-02-24)
    Article
    Restricted access - publisher's policy
    Figueroa-Centeno et al. [4] introduced the following product of digraphs let D be a digraph and let G be a family of digraphs such that V (F) = V for every F¿G. Consider any function h:E(D)¿G. Then the product D¿hG is the ...
  • On the spectrum of the normalized Laplacian of iterated triangulations of graphs 

    Xie, Pinchen; Zhang, Zhongzhi; Comellas Padró, Francesc de Paula (2016-01-15)
    Article
    Open Access
    The eigenvalues of the normalized Laplacian of a graph provide information on its topological and structural characteristics and also on some relevant dynamical aspects, specifically in relation to random walks. In this ...
  • The inverses of some circulant matrices 

    Carmona Mejías, Ángeles; Encinas Bachiller, Andrés Marcos; Gago Álvarez, Silvia; Jiménez Jiménez, M. Jose; Mitjana Riera, Margarida (2015-11-01)
    Article
    Open Access
    We present here necessary and su cient conditions for the invertibility of circulant and symmetric matrices that depend on three parameters and moreover, we explicitly compute the inverse. The techniques we use are related ...
  • Quotient-polynomial graphs 

    Fiol Mora, Miquel Àngel (Elsevier, 2016-01-01)
    Article
    Restricted access - publisher's policy
    As a generalization of orbit-polynomial and distance-regular graphs, we introduce the concept of a quotient-polynomial graph. In these graphs every vertex uinduces the same regular partition around u, where all vertices ...
  • On the number of L-shapes in embedding dimension four numerical semigroups 

    Aguiló Gost, Francisco de Asis L.; García Sánchez, Pedro A.; Llena, David (2015-12-06)
    Article
    Restricted access - publisher's policy
    Minimum distance diagrams, also known as L-shapes, have been used to study some properties related to weighted Cayley digraphs of degree two and embedding dimension three numerical semigroups. In this particular case, it ...
  • The automorphism group of a free-by-cyclic group in rank 2 

    Bogopolski, Oleg; Martino, Armando; Ventura Capell, Enric (2007-05)
    Article
    Open Access
    Let ¡ be an automorphism of a free group F 2 of rank 2 and let M ¡ = F 2 o ¡ Z be the corresponding mapping torus of ¡ . We prove that the group Out ( M ¡ ) is usually virtually cyclic. More- over, ...
  • Locating-dominating sets and identifying codes in Graphs of Girth at least 5 

    Balbuena Martínez, Maria Camino Teófila; Foucaud, Florent; Hansberg Pastor, Adriana (2015-04-29)
    Article
    Open Access
    Locating-dominating sets and identifying codes are two closely related notions in the area of separating systems. Roughly speaking, they consist in a dominating set of a graph such that every vertex is uniquely identified ...
  • Completion and decomposition of a clutter into representable matroids 

    Martí Farré, Jaume; Mier Vinué, Anna de (Elsevier, 2015-05-01)
    Article
    Restricted access - publisher's policy
    This paper deals with the question of completing a monotone increasing family of subsets Gamma of a finite set Omega to obtain the linearly dependent subsets of a family of vectors of a vector space. Specifically, we prove ...

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