Browsing Articles publicats (Matemàtica) by Title
Now showing items 239258 of 263

The null divergence factor
(Universitat Autònoma de Barcelona. Departament de Matemàtiques, 1997)Let (P, Q) be a C 1 vector field defined in a open subset U ⊂ R2 . We call a null divergence factor a C 1 solution V (x, y) of the equation P ∂V + Q ∂V = ∂P + ∂Q V . In previous works ∂x ∂y ∂x ∂y it has been ... 
The power of digraph products applied to labelings
(Elsevier, 2012)The ⊗hproduct was introduced in 2008 by FigueroaCenteno et al. as a way to construct new families of (super) edgemagic graphs and to prove that some of those families admit an exponential number of (super) edgemagic ... 
The problem of distinguishing between a center and a focus for nilpotent and degenerate analytic systems
(Elsevier, 2006)In this work we study the centers of planar analytic vector fields which are limit of linear type centers. It is proved that all the nilpotent centers are limit of linear type centers and consequently the Poincaré–Liapunov ... 
The role of algebraic solutions in planar polynomial differential systems
(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
(Springer, 20190102)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 quotientlike matrix whose entries are ... 
The spectra of subKautz and cyclic Kautz digraphs
(Elsevier, 2017)Kautz digraphs K(d, `) are a wellknown 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 distance1or2 graph is strongly regular
(Taylor & Francis, 20180713)We study regular graphs whose distance2 graph or distance1or2 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 threedimensional center problem for the zeroHopf singularity
(American Institute of Mathematical Sciences, 20160301)In this work we extend wellknown techniques for solving the Poincar\'eLyapunov nondegenerate analytic center problem in the plane to the 3dimensional center problem at the zeroHopf singularity. Thus we characterize the ... 
The unique mixed almost moore graph with parameters k = 2, r = 2 and z = 1
(World Scientific Publishing, 20171102)A natural upper bound for the maximum number of vertices in a mixed graph with maximum undirected degree r, maximum directed outdegree z and diameter k is given by the mixed Moore bound. Graphs with order attaining the ... 
Towards a quantum universe
(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
(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 PoincaréBendixson regions by using transversal conics. We present ... 
Triangle randomization for social network data anonymization
(Society of Mathematicians, Physicists and Astronomers of SloveniaInstitute of Mathematics, Physics, and MechanicsUniversity of Primorska (Slovenia), 20140627)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
(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
(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
(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
(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 ... 
Vaccination is a suitable tool in the control of Aujeszky's disease outbreaks in pigs using a Population Dynamics P systems model
(MDPI, 2020)Aujeszky's disease is one of the main pig viral diseases and results in considerable economic losses in the pork production industry. The disease can be controlled using preventive measures such as improved stock management ... 
Vertex‐transitive graphs that remain connected after failure of a vertex and its neighbors
(Wiley, 2011)A dregular 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 lisogenies of elliptic curves over finite fields: the case l=3
(Universitat Autònoma de Barcelona. Departament de Matemàtiques, 2007)This paper is devoted to the study of the volcanoes of lisogenies 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 ligandtometal concentration ratio in fully labile metalmacromolecular complexation. Easy computations, analytical properties of the currents and graphical method to estimate the stability constant
(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, ...