Ara es mostren els items 1-20 de 99

  • A Boolean algebra approach to the construction of snarks 

    Fiol Mora, Miquel Àngel (John Wiley & Sons, 1991)
    Capítol de llibre
    Accés obert
    This work deals with the construction of snarks, that is, cubic graphs that cannot be 3-edge-colored. A natural generalization of the concept of "color", that describes in a simple way the coloring ("0" or "1") of any set ...
  • A differential approach for bounding the index of graphs under perturbations 

    Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; Garriga Valle, Ernest (2011-03)
    Report de recerca
    Accés obert
  • A differential approach for bounding the index of graphs under perturbations 

    Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; Garriga Valle, Ernest (2011-09-02)
    Article
    Accés obert
    This paper presents bounds for the variation of the spectral radius (G) of a graph G after some perturbations or local vertex/edge modifications of G. The perturbations considered here are the connection of a new vertex ...
  • A discrete optimization problem in local networks and data alignment 

    Fiol Mora, Miquel Àngel; Andrés Yebra, José Luis; Alegre de Miguel, Ignacio; Valero Cortés, Mateo (1987-06)
    Article
    Accés restringit per política de l'editorial
    This paper presents the solution of the following optimization problem that appears in the design of double-loop structures for local networks and also in data memory, allocation and data alignment in SIMD processors. Consider ...
  • A geometric approach to dense Cayley digraphs of finite Abelian groups 

    Aguiló Gost, Francisco de Asis L.; Fiol Mora, Miquel Àngel; Pérez Mansilla, Sonia (Elsevier, 2016)
    Text en actes de congrés
    Accés restringit per política de l'editorial
    We give a method for constructing infinite families of dense (or eventually likely dense) Cayley digraphs of finite Abelian groups. The diameter of the digraphs is obtained by means of the related {\em minimum distance ...
  • A geometric approach to dense Cayley digraphs of finite Abelian groups 

    Aguiló Gost, Francisco de Asis L.; Fiol Mora, Miquel Àngel; Pérez Mansilla, Sonia (2016)
    Article
    Accés restringit per política de l'editorial
    We give a method for constructing infinite families of dense (or eventually likely dense) Cayley digraphs of finite Abelian groups. The diameter of the digraphs is obtained by means of the related minimum distance diagrams. ...
  • A mathematical model for dynamic memory networks 

    Fàbrega Canudas, José; Fiol Mora, Miquel Àngel; Serra Albó, Oriol; Andrés Yebra, José Luis (Iniciativa Digital Politècnica, 2011)
    Text en actes de congrés
    Accés obert
    The aim of this paper is to bring together the work done several years ago by M.A. Fiol and the other authors to formulate a quite general mathematical model for a kind of permutation networks known as dynamic memories. A ...
  • A new approach to the spectral excess theorem for distance-regular graphs 

    Fiol Mora, Miquel Àngel; Gago Álvarez, Silvia; Garriga Valle, Ernest (2009-04-01)
    Article
    Accés obert
    The Spectral Excess Theorem provides a quasi-spectral characterization for a (regular) graph $\Gamma$ with $d+1$ different eigenvalues to be distance-regular graph, in terms of the mean (d-1)-excess of its vertices.\ The ...
  • A note on the order of iterated line digraphs 

    Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel (Wiley, 2016-07-27)
    Article
    Accés obert
    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 ...
  • A simple proof of the spectral excess theorem for distance-regular graphs 

    Fiol Mora, Miquel Àngel; Gago Álvarez, Silvia; Garriga Valle, Ernest (Elsevier, 2010-04-15)
    Article
    Accés restringit per política de l'editorial
    The spectral excess theorem provides a quasi-spectral characterization for a (regular) graph Γ with d+1 distinct eigenvalues to be distance-regular graph, in terms of the excess (number of vertices at distance d) of each ...
  • 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, ...
  • Algebraic characterizations of bipartite distance-regular graphs 

    Fiol Mora, Miquel Àngel (Iniciativa Digital Politècnica, 2011)
    Text en actes de congrés
    Accés obert
    Bipartite graphs are combinatorial objects bearing some interesting symmetries. Thus, their spectra—eigenvalues of its adjacency matrix—are symmetric about zero, as the corresponding eigenvectors come into pairs. Moreover, ...
  • Algebraic characterizations of distance-regular graphs 

    Fiol Mora, Miquel Àngel (Elsevier, 2002)
    Article
    Accés obert
    We survey some old and some new characterizations of distance-regular graphs, which depend on information retrieved from their adjacency matrix. In particular, it is shown that a regular graph with d+1 distinct eigenvalues ...
  • Algebraic Characterizations of Regularity Properties in Bipartite Graphs 

    Abiad Monge, Aida; Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel (2013)
    Article
    Accés restringit per política de l'editorial
    Regular and distance-regular characterizations of general graphs are well-known. In particular, the spectral excess theorem states that a connected graph GG is distance-regular if and only if its spectral excess (a number ...
  • Algunos grafos compuestos 

    Fiol Mora, Miquel Àngel; Fàbrega Canudas, José (Universidad de Barcelona, Departamento de Estadística Matemática;Universidad Politécnica de Barcelona, Escuela Técnica Superior de Arquitectura, Departamento de Matemáticas y Estadística, 1983)
    Article
    Accés obert
    From two graphs $G_1$ and $G_2$ on $N_1$ and $N_2$ vertices respectively, the compound graph $G_1[G_2]$ on $N_1N_2$ vertices is obtained connecting $N_2$ copies of $G_1$ following the structure of $G_2$. We present in ...
  • An algebraic model for the storage of data in parallel memories 

    Fiol Mora, Miquel Àngel; Serra Albó, Oriol (Springer, 1989)
    Capítol de llibre
    Accés obert
    The use of SIMD computers requires efficient schemes of storage of data in order to have conflict-free acces in parallel computation. In this paper we restate the problem of finding such chemes in an algebraic context. ...
  • An eigenvalue characterization of antipodal distance-regular graphs 

    Fiol Mora, Miquel Àngel (1997-11)
    Article
    Accés obert
    Let $\Gamma$ be a regular (connected) graph with $n$ vertices and $d+1$ distinct eigenvalues. As a main result, it is shown that $\Gamma$ is an $r$-antipodal distance-regular graph if and only if the distance graph $\Gamma_d$ ...
  • An interlacing approach for bounding the sum of Laplacian eigenvalues of graphs 

    Abiad, Aida; Fiol Mora, Miquel Àngel; Haemers, Willem H.; Perarnau Llobet, Guillem (2014)
    Text en actes de congrés
    Accés obert
    We apply eigenvalue interlacing techniques for obtaining lower and upper bounds for the sums of Laplacian eigenvalues of graphs, and characterize equality. This leads to generalizations of, and variations on theorems by ...
  • Aplicaciones de la Teoría de Matrices en Matemática Discreta 

    Fiol Mora, Miquel Àngel (1999-07)
    Working paper
    Accés obert
    Se describen algunas aplicaciones de la teoría de matrices a diversos temas pertenecientes al ámbito de la matem\'atica discreta.
  • c-Critical graphs with maximum degree three 

    Fiol Mora, Miquel Àngel (John Wiley and Sons, Inc., 1995)
    Capítol de llibre
    Accés restringit per política de l'editorial
    Let $G$ be a (simple) gtoph with maximum degree three and chromatic index four. A 3-edge-coloring of G is a coloring of its edges in which only three colors are used. Then a vertex is conflicting when some edges incident ...