Recent Submissions

  • Exploiting symmetry on the Universal Polytope 

    Pfeifle, Julián (2012)
    Conference report
    Restricted access - publisher's policy
    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)
    Conference report
    Restricted access - publisher's policy
    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)
    Conference report
    Open Access
    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)
    Conference report
    Open Access
    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)
    Conference report
    Open Access
    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)
    Conference report
    Open Access
    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)
    Conference report
    Open Access
    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)
    Conference report
    Open Access
    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)
    Conference report
    Open Access
    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)
    Conference lecture
    Open Access
    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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