Now showing items 1-20 of 72

    • A description of auto-fixed subgroups in a free group 

      Martino, Armando; Ventura Capell, Enric (2004-06)
      Article
      Open Access
      Let F be a finitely generated free group. By using Bestvina-Handel theory, as well as some further improvements, the eigengroups of a given automorphism of F (and its fixed subgroup among them) are globally analyzed and ...
    • A list of applications of stallings automata 

      Delgado Pin, Jordi; Ventura Capell, Enric (2022-11-22)
      Article
      Open Access
      This survey is intended to be a fast (and reasonably updated) reference for the theory of Stallings automata and its applications to the study of subgroups of the free group, with the main accent on algorithmic aspects. ...
    • A recursive presentation for Mihailova's subgroup 

      Bogopolski, Oleg; Ventura Capell, Enric (2010)
      Article
      Open Access
      We give an explicit recursive presentation for Mihailova's sub- group M(H) of Fn Fn corresponding to a nite, concise and Pei er aspherical presentation H = hx1; : : : ; xn jR1; : : : ;Rmi. This partially answers a ...
    • A Whitehad algorithm for toral relatively hyperbolic groups 

      Kharlampovich, Olga; Ventura Capell, Enric (2012-12-04)
      Article
      Open Access
      The Whitehead problem is solved in the class of toral relatively hyperbolic groups G (i.e. torsion-free relatively hyperbolic groups with abelian parabolic subgroups): there is an algorithm which, given two nite ...
    • Absolute type shaft encoding using LFSR sequences with prescribed length 

      Fuertes Armengol, José Mª; Balle, Borja; Ventura Capell, Enric (2006-02)
      Article
      Open Access
      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 ...
    • 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
      Open Access
      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 ...
    • Algorithmic problems for free-abelian times free groups 

      Delgado Rodríguez, Jordi; Ventura Capell, Enric (2013-10-01)
      Article
      Open Access
      We study direct products of free-abelian and free groups with special emphasis on algorithmic problems. After giving natural extensions of standard notions into that family, we find an explicit expression for an arbitrary ...
    • Algorithmic recognition of infinite cyclic extensions 

      Cavallo, Bren; Delgado Rodríguez, Jordi; Kahrobaei, Delaram; Ventura Capell, Enric (2016-10-25)
      Article
      Open Access
      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 ...
    • 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 ...
    • Autòmats de Stallings, un camí d'anada i tornada 

      Ventura Capell, Enric; Delgado Rodríguez, Jordi (2022-12-14)
      Article
      Open Access
      En aquest article revisem algunes de les propietats fonamentals del grup lliure i fem una exposició detallada de la teoria dels autòmats de Stallings, una interpretació geomètrica dels seus subgrups que ha estat (i segueix ...
    • ÀLGEBRA (Examen 1r quadrimestre) 

      Ventura Capell, Enric (Universitat Politècnica de Catalunya, 2005-11-25)
      Exam
      Restricted access to the UPC academic community
    • ÀLGEBRA (Examen 1r quadrimestre) 

      Ventura Capell, Enric (Universitat Politècnica de Catalunya, 2006-01-13)
      Exam
      Restricted access to the UPC academic community
    • Bounding the gap between a free group (outer) automorphism and its inverse 

      Ladra, Manuel; Silva, Pedro V.; Ventura Capell, Enric (2016-09-01)
      Article
      Open Access
      For any finitely generated group GG , two complexity functions aGaG and ßGßG are defined to measure the maximal possible gap between the norm of an automorphism (respectively, outer automorphism) of GG and the norm ...
    • CÀLCUL (Examen 1r quadrim.) 

      Domènech Blázquez, Margarita; Puente del Campo, María Albina; Rubió Díaz, Pedro; Ventura Capell, Enric (Universitat Politècnica de Catalunya, 2006-01-15)
      Exam
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    • CÀLCUL (Examen 1r quadrim.) 

      Domènech Blázquez, Margarita; Puente del Campo, María Albina; Rubió Díaz, Pedro; Ventura Capell, Enric (Universitat Politècnica de Catalunya, 2006-01-15)
      Exam
      Restricted access to the UPC academic community
    • CÀLCUL (Examen 1r quadrim.) 

      Domènech Blázquez, Margarita; Puente del Campo, María Albina; Rubió Díaz, Pedro; Ventura Capell, Enric (Universitat Politècnica de Catalunya, 2006-01-15)
      Exam
      Restricted access to the UPC academic community
    • CÀLCUL 1 (Examen 1r quadrim) 

      Ventura Capell, Enric; Pons Vallès, Montserrat (Universitat Politècnica de Catalunya, 1996-11-14)
      Exam
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    • CÀLCUL 1 (Examen 1r quadrim) 

      Ventura Capell, Enric (Universitat Politècnica de Catalunya, 2008-12-22)
      Exam
      Restricted access to the UPC academic community
    • CÀLCUL 1 (Examen 1r quadrim) 

      Ventura Capell, Enric; Pons Vallès, Montserrat (Universitat Politècnica de Catalunya, 1999-01-14)
      Exam
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    • CÀLCUL 1 (Examen 1r quadrim) 

      Ventura Capell, Enric; Pons Vallès, Montserrat (Universitat Politècnica de Catalunya, 2004-01-12)
      Exam
      Restricted access to the UPC academic community