Now showing items 21-40 of 59

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

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 ﻿

(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 ﻿

(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 ﻿

(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 ﻿

(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 ﻿

(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 ﻿

(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 ﻿

(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 ﻿

(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 ﻿

(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 ﻿

(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 ﻿

(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 ﻿

(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 ﻿

(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 ﻿

(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 ﻿

(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 ﻿

(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 ﻿

(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 ﻿

(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 ﻿

(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 ...