Exploració per altres contribucions "Universitat Politècnica de Catalunya. MD - Matemàtica Discreta"
Ara es mostren els items 1-20 de 93
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A description of auto-fixed subgroups in a free group
(2004-06)
Article
Accés obertLet 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 lower bound for the size of a Minkowski sum of dilates
(2011-03-01)
Article
Accés obertLet A be a finite non-empty set of integers. An asymptotic estimate of the size of the sum of several dilates was obtained by Bukh. The unique known exact bound concerns the sum |A + k·A|, where k is a prime and |A| is ... -
A note on the degree sequences of graphs with restrictions
(2008-01-15)
Article
Accés obertDegree sequences of some types of graphs will be studied and characterized in this paper. -
A recursive presentation for Mihailova's subgroup
(2010)
Article
Accés obertWe 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 solution to the tennis ball problem
(2005)
Article
Accés obertWe present a complete solution to the so-called tennis ball problem, which is equivalent to counting the number of lattice paths in the plane that use North and East steps and lie between certain boundaries. The solution ... -
A Whitehad algorithm for toral relatively hyperbolic groups
(2012-12-04)
Article
Accés obertThe 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
(2006-02)
Article
Accés obertMaximal-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
(2008-03-31)
Article
Accés obertMaximal-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
(2013-10-01)
Article
Accés obertWe 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
(2016-10-25)
Article
Accés obertWe 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
(2009-04-14)
Text en actes de congrés
Accés obertAbstract-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 ... -
An explicit construction for neighborly centrally symmetric polytopes
(2006-06-29)
Article
Accés obertWe give an explicit construction, based on Hadamard matrices, for an infinite series of $\big\lfloor\frac12\sqrt{d}\big\rfloor$-neighborly centrally symmetric $d$-dimensional polytopes with $4d$~vertices. This ... -
An involution on bicubic maps and beta(0,1)-trees
(2015)
Article
Accés obertBicubic maps are in bijection with (0 ; 1)-trees. We introduce two new ways of decomposing (0 ; 1)-trees. Using this we de ne an endofunc- tion on (0 ; 1)-trees, and thus also on bicubic maps. We show that ... -
Asymptotic enumeration of non-crossing partitions on surfaces
(2013-03-01)
Article
Accés obertWe generalize the notion of non-crossing partition on a disk to general surfaces with boundary. For this, we consider a surface S and introduce the number CS(n) of noncrossing partitions of a set of n points laying on the ... -
Asymptotic study of subcritical graph classes
(2011-12-01)
Article
Accés obertWe present a unified general method for the asymptotic study of graphs from the so-called subcritical graph classes, which include the classes of cacti graphs, outerplanar graphs, and series-parallel graphs. This general ... -
Basis expansions and roots of Ehrhart polynomials
(2004)
Article
Accés obert -
Bijections for Baxter families and related objects
(2011-04)
Article
Accés obertThe Baxter number can be written as $B_n = \sum_0^n \Theta_{k,n-k-1}$. These numbers have first appeared in the enumeration of so-called Baxter permutations; $B_n$ is the number of Baxter permutations of size $n$, and ... -
Bounding the gap between a free group (outer) automorphism and its inverse
(2016-09-01)
Article
Accés obertFor 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 ... -
Bounding the volume of facet-empty lattice tetrahedra
(2005)
Article
Accés obert -
Búsqueda de comunidades en grafos grandes mediante configuraciones implícitas de vectores
(PUBL. UNIVERSIDAD DE ZARAGOZA, 2009)
Text en actes de congrés
Accés obertPresentamos el algoritmo OCA para buscar comunidades solapadas en grafos grandes, como por ejemplo la Wikipedia con 1,6×107 nodos y 1,8×108 aristas. OCA se basa en la búsqueda iterativa de subconjuntos localmente óptimos ...