Now showing items 21-40 of 59

    • Familias infinitas de digrafos de Cayley de grado 2 óptimos sobre grupos abelianos finitos 

      Aguiló Gost, Francisco de Asis L.; Miralles de la Asunción, Alicia (Universidad de Almería, 2012)
      Conference report
      Restricted access - publisher's policy
      Sea GN un grupo abeliano finito de orden N. Para cada conjunto de generadores f, g = GN, consideremos el digrafo de Cayley Cay(GN, {f, g}). Seg´un sea GN c´ıclico o no c´ıclico, podemos obtener un di´ametro ´optimo ...
    • Finite automata for Schreier graphs of virtually free groups 

      Silva, Pedro V.; Soler Escrivà, Xaro; Ventura Capell, Enric (2016-01-01)
      Article
      Open Access
      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 ...
    • Fixed subgroups are compressed in surface groups 

      Zhang, Qiang; Ventura Capell, Enric; Wu, Jianchun (2015-08-01)
      Article
      Open Access
      For a compact surface Sigma (orientable or not, and with boundary or not), we show that the fixed subgroup, Fix B, of any family B of endomorphisms of pi(1)(Sigma) is compressed in pi(1)(Sigma), i.e. rk(Fix B) <= rk(H) for ...
    • Fixed subgroups in direct products of surface groups of Euclidean type 

      Wu, Jianchun; Ventura Capell, Enric; Zhang, Qiang (2020-02-24)
      Article
      Open Access
      We give an explicit characterization of which direct products G of surface groups of Euclidean type satisfy that the fixed subgroup of any automorphism (or endomorphism) of G is compressed, and of which is it always inert.
    • Fusing mobile phone data with other data sources to generate input OD matrices for transport models 

      Montero Mercadé, Lídia; Ros-Roca, Xavier; Herranz, Ricardo; Barceló Bugeda, Jaime (Elsevier, 2019)
      Article
      Open Access
      OD matrices that describe mobility patterns provide major input to most transport analysis models. Since OD matrices are not yet directly observable, they are usually estimated indirectly. Data from new sources such as ...
    • Group-theoretic orbit decidability 

      Ventura Capell, Enric (De Gruytr, 2014-12-01)
      Article
      Open Access
      A recent collection of papers in the last years have given a renovated interest to the notion of orbit decidability. This is a new quite general algorithmic notion, connecting with several classical results, and closely ...
    • Groupoids and Faà di Bruno formulae for Green functions in bialgebras of trees 

      Gálvez Carrillo, Maria Immaculada; Kock, Joachim; Tonks, Andrew (2014)
      Article
      Restricted access - publisher's policy
      We prove a Faà di Bruno formula for the Green function in the bialgebra of P-trees, for any polynomial endofunctor P. The formula appears as relative homotopy cardinality of an equivalence of groupoids.
    • Groupoids and Faà di Bruno Formulae for green functions in bialgebras of trees 

      Gálvez Carrillo, Maria Immaculada; Tonks, Andrew; Kock, Joachim (2012-07)
      External research report
      Open Access
      We prove a Faa di Bruno formula for the Green function in the bialgebra of P-trees, for any polynomial endofunctor P. The formula appears as relative homotopy cardinality of an equivalence of groupoids. For suitable choices ...
    • Grups de simetria del pla i aplicacions 

      Julià Verdaguer, Anna (Universitat Politècnica de Catalunya, 2014-07)
      Bachelor thesis
      Open Access
      L'objectiu d'aquest treball és estudiar i classificar els 17 grups de simetria que existeixen en el pla euclidià. El que es fa és utilitzar coneixements ja adquirits al llarg de la carrera, en assignatures com Geometria ...
    • Intersection problem for Droms RAAGs 

      Delgado Rodríguez, Jorge; Ventura Capell, Enric; Zakharov, Alexander (2018-01-01)
      Article
      Open Access
      We solve the subgroup intersection problem (SIP) for any RAAG G of Droms type (i.e., with defining graph not containing induced squares or paths of length 3): there is an algorithm which, given finite sets of generators ...
    • Inversió d'automorfismes sobre grups 

      Planell Morell, Pere (Universitat Politècnica de Catalunya, 2015-07)
      Bachelor thesis
      Open Access
      L'objectiu del treball és poder mesurar la màxima diferència que hi ha entre la norma d'un automorfisme d'un grup finitament generat $G$ i la norma del seu invers. Per fer-ho construirem normes pels grups $G$, Aut $G$ i ...
    • Irresolubilitat d’un problema d’àlgebra lineal 

      Valls Dellavalle, Oriol (Universitat Politècnica de Catalunya, 2020-07)
      Bachelor thesis
      Open Access
      L'objectiu d'aquest treball és trobar explícitament un subgrup de les matrius 4x4 al que, 2 vectors u i v qualsevols, no es pot decidir l'existència o no d'una matriu A del subgrup tal que Au = v, un problema que podria ...
    • Isomorphisms between graph products of groups 

      Garreta Fontelles, Albert (Universitat Politècnica de Catalunya, 2012-06)
      Master thesis (pre-Bologna period)
      Restricted access - author's decision
      Es donen condicions suficients per tal que la descomposició en producte gràfic d'un grup sigui única.. Un resultat clàssic sobre PC-groups diu que el PC-grup (el grup parcialment commutatiu) G(X) associat a un graf X, ...
    • Lie Markov models with purine/pyrimidine symmetry 

      Fernández Sánchez, Jesús; Sumner, Jeremy; Jarvis, Peter; Woodhams, Michael D. (2013-06)
      External research report
      Open Access
      Continuous-time Markov chains are a standard tool in phylogenetic inference. If homogeneity is assumed, the chain is formulated by specifying time-independent rates of substitutions between states in the chain. In applications, ...
    • Local description of phylogenetic group-based models 

      Casanellas Rius, Marta; Fernández Sánchez, Jesús; Michalek, Mateusz (2013-12)
      External research report
      Open Access
      Motivated by phylogenetics, our aim is to obtain a system of equations that de ne a phylogenetic variety on an open set containing the biologically meaningful points. In this paper we consider phylogenetic varieties de ...
    • On automorphism-fixed subgroups of a free group 

      Martino, Armando; Ventura Capell, Enric (2000-08)
      Article
      Open Access
      Let F be a flnitely generated free group, and let n denote its rank. A subgroup H of F is said to be automorphism-flxed, or auto-flxed for short, if there exists a set S of automorphisms of F such that H is precisely the ...
    • On the natural stabilization of convection dominated problems using high order Bubnov–Galerkin finite elements 

      Cai, Quanji; Kollmannsberger, Stefan; Sala Lardies, Esther; Huerta, Antonio; Rank, Ernst (2014-01)
      Article
      Restricted access - publisher's policy
      In the case of dominating convection, standard Bubnov–Galerkin finite elements are known to deliver oscillating discrete solutions for the convection–diffusion equation. This paper demonstrates that increasing the polynomial ...
    • On the number of solutions of regular systems in sets with positive density in abelian groups 

      Král, Daniel; Serra Albó, Oriol; Vena, Lluis (2010)
      Conference report
      Restricted access - publisher's policy
      We prove a density version for the Ramsey statement that, for fixed r and sufficiently large n, every coloring of an abelian group of order n with r colors has nontrivial monochromatic solutions of the system Ax = 0, where ...
    • 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 ...
    • La presentación del grupo de trenzas 

      Muñoz Gallardo, Sheila (Universitat Politècnica de Catalunya, 2014-07)
      Bachelor thesis
      Open Access
      El objetivo de este proyecto es estudiar la estructura y la presentación de los grupos de trenzas. En la primera parte proporcionaremos un repaso esencial de forma que los conceptos usados en el proyecto estarán previamente ...