Enviaments recents

  • Exploiting symmetry on the Universal Polytope 

    Pfeifle, Julián (2012)
    Text en actes de congrés
    Accés restringit per política de l'editorial
    The most successful method to date for finding lower bounds on the number of simplices needed to triangulate a given polytope P involves optimizing a linear functional over the associated Universal Polytope U(P). However, ...
  • On two distributions of subgroups of free groups 

    Bassino, Frédérique; Martino, Armando; Nicaud, Cyril; Ventura Capell, Enric; Weil, Pascal (Society for Industrial and Applied Mathematics, 2010)
    Text en actes de congrés
    Accés restringit per política de l'editorial
    We study and compare two natural distributions of finitely generated subgroups of free groups. One is based on the random generation of tuples of reduced words; that is the one classically used by group theorists. The ...
  • On the evaluation of the Tutte polynomial at the points (1,-1) and (2,-1) 

    Goodall, Andrew; Merino, Criel; Mier Vinué, Anna de; Noy Serrano, Marcos (2010)
    Text en actes de congrés
    Accés obert
    C. Merino proved recently the following identity between evaluations of the Tutte polynomial of complete graphs: t($K_{n+2}$; 1,−1) = t($K_n$;2,−1). In this work we extend this result by giving a large class of graphs with ...
  • Rotational and dihedral symmetries in Steinhaus and Pascal binary triangles 

    Brunat Blay, Josep Maria; Maureso Sánchez, Montserrat (2010)
    Text en actes de congrés
    Accés obert
    We give explicit formulae for obtaining the binary sequences which produce Steinhaus triangles and generalized Pascal triangles with rotational and dihedral symmetries.
  • An algorithm to design prescribed length codes for single-tracked shaft encoders 

    Balle Pigem, Borja de; Ventura Capell, Enric; Fuertes Armengol, José Mª (2009-04-14)
    Text en actes de congrés
    Accés obert
    Abstract-Maximal-length binary shift register sequences have been known for a long time. They have many interesting properties, one of them is that when taken in blocks of n consecutive positions they form 2n - 1 different ...
  • On polytopality of Cartesian products of graphs 

    Pfeifle, Julián; Pilaud, Vincent; Santos Pérez, Francisco Javier (2010-07)
    Text en actes de congrés
    Accés obert
    We study the polytopality of Cartesian products of non-polytopal graphs. On the one hand, we prove that a product of graphs is the graph of a simple polytope if and only if its factors are. On the other hand, we provide ...
  • Graph operations and Laplacian eigenpolytopes 

    Padrol Sureda, Arnau; Pfeifle, Julián (2010-07)
    Text en actes de congrés
    Accés obert
    We introduce the Laplacian eigenpolytopes ("L-polytopes") associated to a simple undirected graph G, investigate how they change under basic operations such as taking the union, join, complement, line graph and cartesian ...
  • Overlapping community search for social networks 

    Padrol Sureda, Arnau; Perarnau Llobet, Guillem; Pfeifle, Julián; Muntés Mulero, Víctor (IEEE Press. Institute of Electrical and Electronics Engineers, 2010)
    Text en actes de congrés
    Accés obert
    Finding decompositions of a graph into a family of clusters is crucial to understanding its underlying structure. While most existing approaches focus on partitioning the nodes, real-world datasets suggest the presence ...
  • Búsqueda de comunidades en grafos grandes mediante configuraciones implícitas de vectores 

    Muntés Mulero, Víctor; Padrol Sureda, Arnau; Perarnau Llobet, Guillem; Pfeifle, Julián (PUBL. UNIVERSIDAD DE ZARAGOZA, 2009)
    Text en actes de congrés
    Accés obert
    Presentamos el algoritmo OCA para buscar comunidades solapadas en grafos grandes, como por ejemplo la Wikipedia con 1,6×107 nodos y 1,8×108 aristas. OCA se basa en la búsqueda iterativa de subconjuntos localmente óptimos ...
  • Complejos de homomorfismos y disecciones de polígonos 

    Pfeifle, Julián (Secretariado de Publicaciones. Universidad de Valladolid., 2006)
    Comunicació de congrés
    Accés obert
    Encontramos realizaciones canónicas de los complejos politopales Hom(G,H)formados por homomorfismos de grafos y estudiados por Babson y Kozlov. Si G es un grafo completo, caracterizamos en qué casos cierta proyección ...

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