Now showing items 1-20 of 30

  • Activities and coefficients of the Tutte polynomial 

    Hakim, Sahar (Universitat Politècnica de Catalunya, 2019-01)
    Master thesis
    Open Access
    Matroids are combinatorial objects that capture abstractly the essence of dependence. The Tutte polynomial, defined for matroids and graphs, has a numerous amount of information about these structures. In this thesis, we ...
  • A fast and efficient algorithm to identify clusters in networks 

    Comellas Padró, Francesc de Paula; Miralles de la Asunción, Alicia (2008-08-02)
    Article
    Open Access
    A characteristic feature of many relevant real life networks, like the WWW, Internet, transportation and communication networks, or even biological and social networks, is their clustering structure. We discuss in this ...
  • An eigenvalue characterization of antipodal distance-regular graphs 

    Fiol Mora, Miquel Àngel (1997-11)
    Article
    Open Access
    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 $\Gamma_d$ ...
  • Bounded expansion in models of webgraphs 

    Gago Álvarez, Silvia; Schlatter, Dirk (2007-10-02)
    Article
    Open Access
    We study the bounded expansion of several models of web graphs. We show that various deterministic graph models for large complex networks have constant bounded expansion.We study two random models of webgraphs, showing ...
  • Bumblebees: a multiagent combinatorial optimization algorithm inspired by social insect behaviour 

    Comellas Padró, Francesc de Paula; Martínez Navarro, Jesús (2009-01-20)
    Conference lecture
    Open Access
    This paper introduces a multiagent optimization algorithm inspired by the collective behavior of social insects. In our method, each agent encodes a possible solution of the problem to solve, and evolves in a way similar ...
  • Characterizing (l,m)-walk-regularity 

    Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; Garriga Valle, Ernest (2009-05)
    Article
    Open Access
    A graph $\G$ with diameter $D$ and $d+1$ distinct eigenvalues is said to be {\it $(\ell,m)$-walk-regular}, for some integers $\ell\in[0,d]$ and $m\in[0,D]$, $\ell\ge m$, if the number of walks of length $i\in [0,\ell]$ ...
  • Combinatorial vs. algebraic characterizations of pseudo-distance-regularity around a set 

    Cámara Vallejo, Marc; Fàbrega Canudas, José; Fiol Mora, Miquel Àngel; Garriga Valle, Ernest (2009-06)
    External research report
    Open Access
    Given a simple connected graph $\Gamma$ and a subset of its vertices $C$, the pseudo-distance-regularity around $C$ generalizes, for not necessarily regular graphs, the notion of completely regular code. Up to now, most ...
  • Construcció de codis correctors a partir de configuracions i grafs 

    Basart i Muñoz, Josep M. (Universitat Politècnica de Barcelona. Centre de Càlcul, 1986-06)
    Article
    Open Access
    Se trata de presentar algunas de las relaciones de carácter básicamente combinatorio que es posible encontrar entre dos tipos importantes de estructuras de incidencia, como son los grafos simétricos y las t-configuraciones, ...
  • Decomposition spaces, incidence algebras and Möbius inversion 

    Gálvez Carrillo, Maria Immaculada; Kock, Joachim; Tonks, Andrew (2014-04-11)
    External research report
    Open Access
  • Decomposition spaces, incidence algebras and Möbius inversion I: basic theory 

    Gálvez Carrillo, Maria Immaculada; Kock, Joachim; Tonks, Andrew (2015-12)
    External research report
    Open Access
    This is the first in a series of papers devoted to the theory of decomposition spaces, a general framework for incidence algebras and Möbius inversion, where algebraic identities are realised by taking homotopy cardinality ...
  • Decomposition spaces, incidence algebras and Möbius inversion II: completeness, length filtration, and finiteness 

    Gálvez Carrillo, Maria Immaculada; Kock, Joachim; Tonks, Andrew (2015-12)
    External research report
    Open Access
    This is part 2 of a trilogy of papers introducing and studying the notion of decomposition space as a general framework for incidence algebras and Möbius inversion, with coefficients in 8-groupoids. A decomposition space ...
  • Decomposition spaces, incidence algebras and Möbius inversion III: the decomposition space of Möbius intervals 

    Gálvez Carrillo, Maria Immaculada; Kock, Joachim; Tonks, Andrew (2015-12)
    External research report
    Open Access
    Decomposition spaces are simplicial 8-groupoids subject to a certain exactness condition, needed to induce a coalgebra structure on the space of arrows. Conservative ULF functors between decomposition spaces induce coalgebra ...
  • Decomposition spaces in combinatorics 

    Gálvez Carrillo, Maria Immaculada; Kock, Joachim; Tonks, Andrew (2016-12)
    External research report
    Open Access
    A decomposition space (also called unital 2-Segal space) is a simplicial object satisfying an exactness condition weaker than the Segal condition: just as the Segal condition expresses (up to homotopy) composition, the new ...
  • Enumeration and random generation of planar maps 

    Geffner Fuenmayor, Ivan Eduardo (Universitat Politècnica de Catalunya, 2014-07)
    Master thesis
    Open Access
    This works gives some results on outerplanar maps, which includes a codification of simple outerplanar maps with 3n bits, where n is the number of nodes. It also includes an algorithm to produce random generated maps with ...
  • Euler: Idees seminals en combinatòria 

    Brunat Blay, Josep Maria (2007-06-20)
    Audiovisual
    Open Access
    De la quantitat ingent de treballs d'Euler, només una part molt minsa està dedicada a la combinatòria. Tanmateix, els pocs problemes combinatoris que Euler tractà han estat punt d'arrencada de desenvolupaments posteriors ...
  • Genealogía de permutaciones simples de orden una potencia de dos 

    Acosta Humánez, Primitivo Belén (2006-02)
    Article
    Open Access
    The aim of this paper is to show some properties of simple permutations with order a power of two and to give a combinatorial formula to determine its genealogy involving two new operations: the \textit{pasting} operation ...
  • Matricial realizations of the solutions of the Carlson problem 

    Compta Creus, Albert; Ferrer Llop, Josep (2001)
    Article
    Open Access
    The Klein theorem asserts the existence of a solution of the Carlson problem when a related Littelewood-Richardson sequence exists. Here we present an explicit construction of these matricial solutions.
  • Modeling complex networks with self-similar outerplanar unclustered graphs 

    Comellas Padró, Francesc de Paula; Miralles de la Asunción, Alicia (2009-01-21)
    Article
    Open Access
    This paper introduces a family of modular, self-similar, small-world graphs with clustering zero. Relevant properties of this family are comparable to those of some networks associated with technological systems with a low ...
  • On monochromatic solutions of equations in groups 

    Cameron, Peter J.; Cilleruelo, Javier; Serra Albó, Oriol (2006-01-12)
    Article
    Open Access
    Resum no disponible
  • Planar unclustered graphs to model technological and biological networks 

    Miralles de la Asunción, Alicia; Chen, Lichao; Zhang, Zhongzhi; Comellas Padró, Francesc de Paula (2009-02-25)
    Article
    Open Access
    Many real life networks present an average path length logarithmic with the number of nodes and a degree distribution which follows a power law. Often these networks have also a modular and self-similar structure and, in ...