Enviaments recents

  • 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 ...
  • Put three and three together: Triangle-driven community detection 

    Prat Pérez, Arnau; Domínguez Sal, David; Brunat Blay, Josep Maria; Larriba Pey, Josep (Association for Computing Machinery (ACM), 2016-02-01)
    Article
    Accés obert
    Community detection has arisen as one of the most relevant topics in the field of graph data mining due to its applications in many fields such as biology, social networks, or network traffic analysis. Although the existing ...
  • Polygons as sections of higher-dimensional polytopes 

    Padrol Sureda, Arnau; Pfeifle, Julián (2015-02-09)
    Article
    Accés obert
    We show that every heptagon is a section of a 3-polytope with 6 vertices. This implies that every n-gon with n >= 7 can be obtained as a section of a (2 + [n/7])-dimensional polytope with at most [6n/7] vertices; and ...
  • Lower bounds on the maximum number of non-crossing acyclic graphs 

    Huemer, Clemens; Mier Vinué, Anna de (2015-08-01)
    Article
    Accés restringit per política de l'editorial
    This paper is a contribution to the problem of counting geometric graphs on point sets. More concretely, we look at the maximum numbers of non-crossing spanning trees and forests. We show that the so-called double chain ...
  • Finite automata for Schreier graphs of virtually free groups 

    Silva, Pedro V.; Soler Escrivà, Xaro; Ventura Capell, Enric (2016-01-01)
    Article
    Accés restringit per política de l'editorial
    The Stallings construction for f.g. subgroups of free groups is generalized by introducing the concept of Stallings section, which allows efficient computation of the core of a Schreier graph based on edge folding. It is ...
  • On the probability of planarity of a random graph near the critical point 

    Noy Serrano, Marcos; Ravelomanana, Vlady; Rue, Juanjo (2015-03-01)
    Article
    Accés obert
    Let G(n, M) be the uniform random graph with n vertices and M edges. Erdos and Renyi (1960) conjectured that the limiting probability; lim(n ->infinity) Pr{G(n, n/2) is planar}; exists and is a constant strictly between 0 ...
  • The automorphism group of a free-by-cyclic group in rank 2 

    Bogopolski, Oleg; Martino, Armando; Ventura Capell, Enric (2007-05)
    Article
    Accés obert
    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, ...
  • Absolute-type shaft encoding using LFSR sequences with a prescribed length 

    Fuertes Armengol, José Mª; Balle Pigem, Borja de; Ventura Capell, Enric (2008-03-31)
    Article
    Accés obert
    Maximal-length binary sequences have existed for a long time. They have many interesting properties, and one of them is that, when taken in blocks of n consecutive positions, they form 2n - 1 different codes in a closed ...
  • Absolute type shaft encoding using LFSR sequences with prescribed length 

    Fuertes Armengol, José Mª; Balle, Borja; Ventura Capell, Enric (2006-02)
    Article
    Accés obert
    Maximal-length binary 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 2 n ° 1 diÆerent codes in a ...
  • Completion and decomposition of a clutter into representable matroids 

    Martí Farré, Jaume; Mier Vinué, Anna de (Elsevier, 2015-05-01)
    Article
    Accés restringit per política de l'editorial
    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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