Now showing items 224-243 of 244

    • The role of algebraic solutions in planar polynomial differential systems 

      Giacomini, Héctor; Giné, Jaume; Grau Montaña, Maite (Cambridge University Press, 2007)
      We study a planar polynomial differential system, given by . We consider a function , where gi(x) are algebraic functions of with ak(x) and algebraic functions, A0(x,y) and A1(x,y) do not share any common factor, h2(x) is ...
    • The spectra of lifted digraphs 

      Dalfó, Cristina; Fiol, Miguel Angel; Sirán, Jozef (Springer, 2019-01-02)
      We present a method to derive the complete spectrum of the lift Γα of a base digraph Γ , with voltage assignment α on a (finite) group G. The method is based on assigning to Γ a quotient-like matrix whose entries are ...
    • The spectra of subKautz and cyclic Kautz digraphs 

      Dalfó, Cristina (Elsevier, 2017)
      Kautz digraphs K(d, `) are a well-known family of dense digraphs, widely studied as a good model for interconnection networks. Closely related with these, the cyclic Kautz CK(d, `) and the subKautz sK(d, 2) digraphs were ...
    • The spectral excess theorem for graphs with few eigenvalues whose distance- 2 or distance-1-or-2 graph is strongly regular 

      Dalfó, Cristina; Fiol, Miguel Angel; Koolen, Jack (Taylor & Francis, 2018-07-13)
      We study regular graphs whose distance-2 graph or distance-1-or-2 graph is strongly regular. We provide a characterization of such graphs Γ (among regular graphs with few distinct eigenvalues) in terms of the spectrum and ...
    • The three-dimensional center problem for the zero-Hopf singularity 

      García, I. A. (Isaac A.); Valls, Claudia (American Institute of Mathematical Sciences, 2016-03-01)
      In this work we extend well-known techniques for solving the Poincar\'e-Lyapunov nondegenerate analytic center problem in the plane to the 3-dimensional center problem at the zero-Hopf singularity. Thus we characterize the ...
    • The unique mixed almost moore graph with parameters k = 2, r = 2 and z = 1 

      Buset, Dominique; López Lorenzo, Ignacio; Miret, Josep M. (Josep Maria) (World Scientific Publishing, 2017-11-02)
      A natural upper bound for the maximum number of vertices in a mixed graph with maximum undirected degree r, maximum directed out-degree z and diameter k is given by the mixed Moore bound. Graphs with order attaining the ...
    • Towards a quantum universe 

      Giné, Jaume (Springer Verlag, 2012)
      In this short review we study the state of the art of the great problems in cosmology and their interrelationships. The reconciliation of these problems passes undoubtedly through the idea of a quantum universe.
    • Transversal conics and the existence of limit cycles 

      Giacomini, Héctor; Grau Montaña, Maite (Elsevier, 2015)
      This paper deals with the problem of location and existence of limit cycles for real planar polynomial differential systems. We provide a method to construct Poincaré-Bendixson regions by using transversal conics. We present ...
    • Triangle randomization for social network data anonymization 

      Brankovic, Ljiljana; López Lorenzo, Ignacio; Miller, Mirka; Sebé Feixas, Francesc (Society of Mathematicians, Physicists and Astronomers of SloveniaInstitute of Mathematics, Physics, and MechanicsUniversity of Primorska (Slovenia), 2014-06-27)
      In order to protect privacy of social network participants, network graph data should be anonymised prior to its release. Most proposals in the literature aim to achieve $k$-anonymity under specific assumptions about the ...
    • Trisection for supersingular genur 2 curves in characteristic 2 

      Miret, Josep M. (Josep Maria); Pujolàs Boix, Jordi; Thériault, Nicolas (American Institute of Mathematical Sciences (AIMS), 2014)
      By reversing reduction in divisor class arithmetic we provide efficient trisection algorithms for Jacobians of supersingular genus 2 curves over finite fields of characteristic 2. With our technique we obtain new results ...
    • Two different epidemiological scenarios of border disease in the populations of Pyrenean chamois (Rupicapra p. pyrenaica) after the first disease outbreaks 

      Fernández Sirera, Laura; Cabezón Ponsoda, Óscar; Allepuz Palau, Alberto; Rosell Bellsola, Rosa; Riquelme Guerrero, Cristina; Serrano Ferrón, Emmanuel; Lavín González, Santiago; Marco Sánchez, Ignasi (Public Library of Science, 2012)
      Since 2001 several outbreaks of a new disease associated with Border disease virus (BDV) infection have caused important declines in Pyrenean chamois (Rupicapra pyrenaica) populations in the Pyrenees. The goal of this ...
    • Universal centers and composition conditions 

      Giné, Jaume; Grau Montaña, Maite; Llibre, Jaume (London Mathematical Society, 2013)
      In this paper, we characterize the universal centres of the ordinary differential equations , where ai(θ) are trigonometric polynomials, in terms of the composition conditions. These centres are closely related with the ...
    • Universal centers in the cubic trigonometric Abel equation 

      Giné, Jaume; Grau Montaña, Maite; Santallusia Esvert, Xavier (Bolyai Institute. University of SzegedHungarian Academy of Sciences, 2014)
      We study the center problem for the trigonometric Abel equation dρ/dθ=a1(θ)ρ2+a2(θ)ρ3,dρ/dθ=a1(θ)ρ2+a2(θ)ρ3, where a1(θ)a1(θ) and a2(θ)a2(θ) are cubic trigonometric polynomials in θθ. This problem is closely connected with ...
    • Vertex‐transitive graphs that remain connected after failure of a vertex and its neighbors 

      Hamidoune, Yahya Ould; Lladó, A.; López Masip, Susana-Clara (Wiley, 2011)
      A d-regular graph is said to be superconnected if any disconnecting subset with cardinality at most d is formed by the neighbors of some vertex. A superconnected graph that remains connected after the failure of a vertex ...
    • Volcanoes of l-isogenies of elliptic curves over finite fields: the case l=3 

      Miret, Josep M. (Josep Maria); Sadornil Renedo, Daniel; Tena Ayuso, Juan; Tomàs Cuñat, Rosa Ana; Valls Marsal, Magda (Universitat Autònoma de Barcelona. Departament de Matemàtiques, 2007)
      This paper is devoted to the study of the volcanoes of l-isogenies of elliptic curves over a finite field, focusing on their height as well as on the location of curves across its different levels. The core of the paper ...
    • Voltammetric currents for any ligand-to-metal concentration ratio in fully labile metal-macromolecular complexation. Easy computations, analytical properties of the currents and graphical method to estimate the stability constant 

      Galceran i Nogués, Josep; Cecilia Averós, Joan; Salvador, José; Monné Esquerda, Josep; Torrent, Marià; Companys Ferran, Encarnació; Puy Llorens, Jaume; Garcés, Josep Lluís; Mas i Pujadas, Francesc (Elsevier, 1999)
      In order to enable a wider use of voltammetric methods in speciation analysis, it is convenient not to be restricted by ligand excess conditions. This work assumes labile ideal complexation of a metal ion by a ligand, ...
    • Voltammetric lability of metal complexes at spherical micorelectrodes with various radii 

      Galceran i Nogués, Josep; Puy Llorens, Jaume; Salvador, José; Cecilia Averós, Joan; Leeuwen, Herman P. van (Elsevier, 2001)
      The size of a microelectrode can have a dramatic impact on the relative importance of the diffusional and kinetic contributions to the voltammetric current of an electroactive metal ion in a complexing medium. Decreasing ...
    • Voltammetric lability of multiligand complexes: the case of ML2 

      Puy Llorens, Jaume; Cecilia Averós, Joan; Galceran i Nogués, Josep; Town, Raewyn M.; Leeuwen, Herman P. van (Elsevier, 2004)
      The voltammetric lability of a complex system, where a metal ion M and a ligand L form the species ML and ML2, is examined. Together with the rigorous numerical simulation of the problem, two limiting cases are analysed ...
    • Weierstrass integrability in Liénard differential systems 

      Giné, Jaume; Llibre, Jaume (Elsevier, 2011)
      In this work we study the Liénard differential systems that admit a Weierstrass first integral or a Weierstrass inverse integrating factor
    • Weierstrass integrability of differential equations 

      Giné, Jaume; Grau Montaña, Maite (Elsevier, 2010)
      The integrability problem consists in finding the class of functions a first integral of a given planar polynomial differential system must belong to. We recall the characterization of systems which admit an elementary or ...