Now showing items 1-20 of 100

    • A branch-and-price algorithm for the Aperiodic Multi-Period Service Scheduling Problem 

      Fernández Aréizaga, Elena; Kalcsics, Jörg; Núñez del Toro, Alma Cristina (Elsevier, 2017-12-16)
      Article
      Open Access
      This paper considers the multi-period service scheduling problem with an aperiodic service policy. In this problem, a set of customers who periodically require service over a finite time horizon is given. To satisfy the ...
    • A connection between Inverse Problems and Nonstandard Analysis 

      Martínez Moraian, Alejandra (Universitat Politècnica de Catalunya, 2018-10)
      Master thesis
      Restricted access - author's decision
      Nonstandard analysis was born in the decade of 1960 an attempt to give a formal context to the Leibniz approach to differential calculus, in particular in order to provide a rigorous foundation to the notions of infinitesimal ...
    • 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 ...
    • A finite version of the Kakeya problem 

      Ball, Simeon Michael; Blokhuis, Aart; Domenzain, Diego (2016-06-02)
      Article
      Open Access
      Let L be a set of lines of an affine space over a field and let S be a set of points with the property that every line of L is incident with at least N points of S. Let D be the set of directions of the lines of L considered ...
    • A general method to obtain the spectrum and local spectra of a graph from its regular partitions 

      Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel (2020-07-12)
      Article
      Open Access
      It is well known that, in general, part of the spectrum of a graph can be obtained from the adjacency matrix of its quotient graph given by a regular partition. In this paper, a method that gives all the spectrum, and also ...
    • A unified formal framework for factorial and probabilistic topic modelling 

      Gibert, Karina; Hernández Potiomkin, Yaroslav (Multidisciplinary Digital Publishing Institute (MDPI), 2023-10-21)
      Article
      Open Access
      Topic modelling has become a highly popular technique for extracting knowledge from texts. It encompasses various method families, including Factorial methods, Probabilistic methods, and Natural Language Processing methods. ...
    • 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 ...
    • Additive volume of sets contained in few arithmetic progressions 

      Freiman, Gregory A.; Serra Albó, Oriol; Spiegel, Christoph (De Gruyter, 2019-03-06)
      Article
      Open Access
      A conjecture of Freiman gives an exact formula for the largest volume of a finite set A of integers with given cardinality k=|A| and doubling T=|2A|. The formula is known to hold when T=3k-4, for some small range over 3k-4 ...
    • An algebraic fractal approach to Collatz Conjecture 

      Martín Chabrera, Víctor (Universitat Politècnica de Catalunya, 2019-05)
      Bachelor thesis
      Open Access
      The Collatz conjecture is one of the most easy-to-state unsolved problems in Mathematics today. It states that after a finite number of iterations of the Collatz function, defined by C(n) = n/2 if n is even, and by C(n) = ...
    • An algebraic framework for Diffie-Hellman assumptions 

      Escala Ribas, Alex; Herold, Gottfried; Kiltz, Eike; Ràfols Salvador, Carla; Villar Santos, Jorge Luis (2017-01)
      Article
      Open Access
      We put forward a new algebraic framework to generalize and analyze Di e-Hellman like Decisional Assumptions which allows us to argue about security and applications by considering only algebraic properties. Our D`;k-MDDH ...
    • An analogue of Vosper's theorem for extension fields 

      Bachoc, Christine; Serra Albó, Oriol; Zemor, Gilles (2017-11-01)
      Article
      Open Access
      We are interested in characterising pairs S, T of F-linear subspaces in a field extension L/F such that the linear span ST of the set of products of elements of S and of elements of T has small dimension. Our central result ...
    • 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 $\Gamma_d$ ...
    • Anticyclotomic p-adic L-functions and the exceptional zero phenomenon 

      Molina Blanco, Santiago (2019-08-15)
      Article
      Open Access
      Let A be a modular elliptic curve over a totally real field F, and let E/F be a totally imaginary quadratic extension. In the event of exceptional zero phenomenon, we prove a formula for the derivative of the multivariable ...
    • Approximation schemes for randomly sampling colorings 

      González I Sentís, Marta (Universitat Politècnica de Catalunya, 2019-10)
      Master thesis
      Open Access
      Graph colouring is arguably one of the most important issues in Graph Theory. However, many of the questions that arise in the area such as the chromatic number problem or counting the number of proper colorings of a graph ...
    • Asymptotics in the schema of simple varieties of trees 

      Garrido Pérez, Iñaki (Universitat Politècnica de Catalunya, 2022-05)
      Master thesis
      Open Access
      We study the functional equation y(x) = xA(y(x)) satisfied by the generating functions in the schema of simple varieties of trees. The radii of convergence r, R of y, A respectively satisfy y(r) <= R. In the subcritical ...
    • Big Ramsey degrees of 3-uniform hypergraphs 

      Balko, Martin; Chodounsky, David; Hubicka, Jan; Konecny, Matej; Vena Cros, Lluís (2019)
      Conference report
      Open Access
      Given a countably infinite hypergraph $\mathcal R$ and a finite hypergraph $\mathcal A$, the \emph{big Ramsey degree} of $\mathcal A$ in $\mathcal R$ isthe least number $L$ such that, for every finite $k$ and every ...
    • 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 ...
    • Center of maximum-sum matchings of bichromatic points 

      Pérez Lantero, Pablo; Seara Ojea, Carlos (Elsevier, 2024-03-01)
      Article
      Restricted access - publisher's policy
      Let R and B be two point sets in the plane with . Let be a perfect matching that matches points of R with points of B and maximizes , the total Euclidean distance of the matched pairs. In this paper, we prove that there ...
    • Characterizations of classes of graphs by forbidden minors 

      Böhmová, Katerina (Universitat Politècnica de Catalunya, 2011)
      Master thesis
      Open Access
      En aquest treball tractem el problema de descriure classes de grafs especificades per un menor prohibit. Concretament, presentem resultats de Wagner que caracteritzen grafs sense K5 o bé K3,3 com a menor. També donem ...