Ara es mostren els items 13-32 de 32

    • Global phase portraits of the quadratic systems having a singular and irreducible invariant curve of degree 3 

      Pantazi, Chara; Llibre Saló, Jaume (2023-01)
      Article
      Accés obert
      Any singular irreducible cubic curve (or simply, cubic) after an affine transformation can be written as either y2=x3 , or y2=x2(x+1) , or y2=x2(x-1) . We classify the phase portraits of all quadratic polynomial differential ...
    • Integrability and dynamics of a simplified class B laser system 

      Llibre Saló, Jaume; Pantazi, Chara (American Institute of Physics (AIP), 2023-10-12)
      Article
      Accés obert
      A simplified class B laser system is a family of differential polynomial systems of degree two depending on the parameters a and b. Its rich dynamics has already been observed in 1980s, see Arecchi et al. [Opt. Commun. 51, ...
    • Integrability and linearizability of a family of three-dimensional quadratic systems 

      Pantazi, Chara; Amen, Azad; Aziz, Waleed (2021-01-01)
      Article
      Accés obert
      We consider a three-dimensional vector field with quadratic nonlinearities and in general none of the axis plane is invariant. For our investigation, we are interesting in the case of (1:-2:1) – resonance at the origin. ...
    • Invariant algebraic surfaces of polynomial vector fields in dimension three 

      Kruff, Niclas; Llibre Saló, Jaume; Pantazi, Chara; Walcher, Sebastian (Springer, 2021-01-01)
      Article
      Accés obert
      We discuss criteria for the nonexistence, existence and computation of invariant algebraic surfaces for three-dimensional complex polynomial vector fields, thus transferring a classical problem of Poincaré from dimension ...
    • Limit cycles bifurcating from a degenerate center 

      Llibre Saló, Jaume; Pantazi, Chara (2016-02-01)
      Article
      Accés obert
      We study the maximum number of limit cycles that can bifurcate from a degenerate center of a cubic homogeneous polynomial differential system. Using the averaging method of second order and perturbing inside the class of ...
    • Morphisms and inverse problems 

      Christopher, Colin; Llibre Saló, Jaume; Pantazi, Chara; Walcher, Sebastian (2011-11-03)
      Report de recerca
      Accés obert
      In order to investigate polynomial vector ¯elds admitting a prescribed Darboux integrating factor, we show that it is helpful to employ morphisms of the a±ne plane. In particular, such morphisms may be used to remove ...
    • Morphisms and inverse problems for Darboux integrating factors 

      Llibre Saló, Jaume; Pantazi, Chara; Walcher, Sebastian (2013-12)
      Article
      Accés obert
      Polynomial vector fields which admit a prescribed Darboux integrat- ing factor are quite well-understood when the geometry of the underlying curve is nondegenerate. In the general setting morphisms of the affine plane ...
    • On planar polynomial vector fields with elementary first integrals 

      Christopher, Colin; Pantazi, Chara; Llibre Saló, Jaume; Walcher, Sebastian (2019-10-05)
      Article
      Accés obert
      We show that under rather general conditions a polynomial differential system having an elementary first integral already must admit a Darboux first integral, and we explicitly characterize the vector fields in this class. ...
    • On the integrability of polynomial fields in the plane by means of Picard-Vessiot theory 

      Lázaro Ochoa, José Tomás; Morales Ruíz, Juan José; Acosta Humánez, Primitivo Belén; Pantazi, Chara (2012-01-12)
      Report de recerca
      Accés obert
      We study the integrability of polynomial vector fields using Galois theory of linear differential equations when the associated foliations is reduced to a Riccati type foliation. In particular we obtain integrability results ...
    • On the integrability of polynomial vector fields in the plane by means of Picard-Vessiot theory 

      Acosta-Humànez, Primitivo; Lázaro Ochoa, José Tomás; Morales Ruiz, Juan José; Pantazi, Chara (American Institute of Mathematical Sciences, 2015-05-01)
      Article
      Accés obert
      We study the integrability of polynomial vector fields using Galois theory of linear differential equations when the associated foliations is reduced to a Riccati type foliation. In particular we obtain integrability results ...
    • Online engineering mathematics course : development and implementation of a successful project 

      Soares, Filomena; Lopes, Ana Paula; Cellmer, Anna; Uukkivi, Anne; Serrat Piè, Carles; Pantazi, Chara; Feniser, Cristina; Safiulina, Elena; Serdean, Florina M.; Kierkosz, Igor; Kelly, Gerald; Cymerman, Joanna; Brown, Ken; Alier Forment, Marc; Bruguera Padró, Maria Montserrat; Estela Carbonell, M. Rosa; Labanova, Oksana; Bocanet, Vlad I.; Volodymyr, Sushch; Martin, Errol (International Association of Technology, Education and Development (IATED), 2022)
      Comunicació de congrés
      Accés obert
      According to the New UNESCO global survey studying the effect of Covid-19 on higher education (2021) the pandemic has had an impact on higher education systems in terms of access and quality of teaching and learning. ...
    • Phase portraits of separable Hamiltonian systems 

      Guillamon Grabolosa, Antoni; Pantazi, Chara (Universidad de Sevilla, 2007-09)
      Text en actes de congrés
      Accés obert
      We study some generalizations of potential Hamiltonian systems $(H(x, y) = y^2 + F(x))$ with one degree of freedom. In particular, we are interested in Hamiltonian systems with Hamiltonian functions of type $H(x, y) = ...
    • Polynomial differential systems having a given Darbouxian first integral 

      Llibre Saló, Jaume; Pantazi, Chara (Elsevier, 2004)
      Article
      Accés obert
      The Darbouxian theory of integrability allows to determine when a polynomial differential system in C2 has a first integral of the kind f λ1 1 ···f λp p exp(g/h) where fi , g and h are polynomials in C[x, y], and λi ∈ C ...
    • Pràctiques de Minitab, problemes guia i preguntes d'autoavaluacions 

      Ferrer Biosca, Alberto; Pantazi, Chara; Serrat Piè, Carles (Universitat Politècnica de Catalunya, 2015-09-28)
      Apunts
      Accés obert
    • Qualitative study of a model with Rastall gravity 

      Pantazi, Chara; Llibre Saló, Jaume (2020-12-17)
      Article
      Accés obert
      We consider the Rastall theory for the flat Friedmann-Robertson-Walker Universe filled with a perfect fluid that satisfies a linear equation of state. The corresponding dynamical system is a two dimensional system of ...
    • Semiclassical quantification of some two degree of freedom potentials: A differential Galois approach 

      Acosta Humánez, Primitivo Belen; Lázaro Ochoa, José Tomás; Pantazi, Chara; Morales Ruiz, Juan José (2024-01-01)
      Article
      Accés obert
      In this work we explain the relevance of the Differential Galois Theory in the semiclassical (or WKB) quantification of some two degree of freedom potentials. The key point is that the semiclassical path integral quantification ...
    • Some inverse problems 

      Christopher, Colin; Llibre Saló, Jaume; Pantazi, Chara; Walcher, Sebastian (2011-07-06)
      Report de recerca
      Accés restringit per política de l'editorial
      The Darboux theory of integrability for planar polynomial di®erential equations is a classical ¯eld, with connections to Lie symmetries, di®erential algebra and other areas of mathematics. In the present paper we introduce ...
    • Symmetries of homogeneous cosmologies 

      Cotsakis, Spiros; Leach, P. G. L.; Pantazi, Chara (2004)
      Article
      Accés obert
      We reformulate the dynamics of homogeneous cosmologies with a scalar field matter source with an arbitrary self- interaction potential in the language of jet bundles and extensions of vector fields. In this framework, the ...
    • The Picard-Fuchs equations for complete hyperelliptic integrals of even order curves, and the actions of the generalized Neumann system 

      Fedorov, Yuri; Pantazi, Chara (2014-03-01)
      Article
      Accés obert
      We consider a family of genus 2 hyperelliptic curves of even order and obtain explicitly the systems of 5 linear ordinary differential equations for periods of the corresponding Abelian integrals of first, second, and third ...
    • Three-dimensional Lotka–Volterra systems with 3:-1:2-resonance 

      Aziz, Waleed; Christopher, Colin; Llibre Saló, Jaume; Pantazi, Chara (2021-08)
      Article
      Accés obert
      We study the local integrability at the origin of a nine-parameter family of three-dimensional Lotka–Volterra differential systems with (3:- 1:2)-resonance. We give necessary and sufficient conditions on the parameters of ...