Ara es mostren els items 1-20 de 22

    • A contact geometry framework for field theories with dissipation 

      Gaset Rifà, Jordi; Gràcia Sabaté, Francesc Xavier; Muñoz Lecanda, Miguel Carlos; Rivas Guijarro, Xavier; Román Roy, Narciso (2020-03-01)
      Article
      Accés obert
      We develop a new geometric framework suitable for dealing with Hamiltonian field theories with dissipation. To this end we define the notions of k-contact structure and k-contact Hamiltonian system. This is a generalization ...
    • Bifurcation at complex instability 

      Ollé Torner, Mercè; Pfenniger, Daniel (1995)
      Article
      Accés obert
      In an autonomous Hamiltonian system with three or more degrees of freedom, a family of periodic orbits may become unstable when two pairs of characteristic multipliers coallesce on the unit circle at points not equal to ...
    • Central configurations on the charged three-body problem 

      Perez-Chavela, Ernesto; Susín Sánchez, Antonio; Yan, Zhiming A. (1996)
      Capítol de llibre
      Accés obert
    • Centre and isochronicity conditions for systems with homogeneous nonlinearities 

      Gasull Embid, Armengol; Guillamon Grabolosa, Antoni; Mañosa Fernández, Víctor (1995)
      Article
      Accés obert
      We study the centre-focus problem for systems with homogeneous nonlinearities. In the centre case we study the characterization of the isochronous centres. More explicitly, we derive six necessary conditions to be a ...
    • Constant sigma_2-curvature metrics with non isolated singularities 

      Muixí Ballonga, Alba (Universitat Politècnica de Catalunya, 2016-10)
      Projecte Final de Màster Oficial
      Accés restringit per decisió de l'autor
      The aim of this thesis is to give a method to produce families of complete Riemannian metrics with positive constant $\sigma_k$-curvature equal to $2^{-k}\binom{n}{k}$ on $M\setminus \Lambda^p$, where $M$ is a Riemannian ...
    • Effective reducibility of quasiperiodic linear equations close to constant coefficients 

      Jorba, Angel; Ramírez Ros, Rafael; Villanueva Castelltort, Jordi (1995)
      Article
      Accés obert
      Let us consider the differential equation $$ \dot{x}=(A+\varepsilon Q(t,\varepsilon))x, \;\;\;\; |\varepsilon|\le\varepsilon_0, $$ where $A$ is an elliptic constant matrix and $Q$ depends on time in a quasiperiodic ...
    • Effective stability and KAM theory 

      Delshams Valdés, Amadeu; Gutiérrez Serrés, Pere (1995)
      Article
      Accés obert
      The two main stability results for nearly integrable Hamiltonian systems are revisited: Nekhoroshev theorem, concerning exponential lower bounds for the stability time (effective stability), and KAM theorem, concerning ...
    • Estimates on invariant tori near an elliptic equilibrium point of a Hamiltonian system 

      Delshams Valdés, Amadeu; Gutiérrez Serrés, Pere (1996)
      Article
      Accés obert
      We give a precise statement for KAM theorem in a neighbourhood of an elliptic equilibrium point of a Hamiltonian system. If the frequencies of the elliptic point are nonresonant up to a certain order $K\ge4$, and a ...
    • Exponentially small splitting of separatrices for perturbed integrable standard-like maps 

      Delshams Valdés, Amadeu; Ramírez Ros, Rafael (1997)
      Article
      Accés obert
      We consider fast quasiperiodic perturbations with two frequencies $(1/\varepsilon,\gamma/\varepsilon)$ of a pendulum, where $\gamma$ is the golden mean number. The complete system has a two-dimensional invariant ...
    • Exponentially small splitting of separatrices under fast quasiperiodic forcing 

      Delshams Valdés, Amadeu; Gelfreich, Vassili; Jorba, Angel; Martínez-Seara Alonso, M. Teresa (1997)
      Article
      Accés obert
      We consider fast quasiperiodic perturbations with two frequencies $(1/\varepsilon,\gamma/\varepsilon)$ of a pendulum, where $\gamma$ is the golden mean number. The complete system has a two-dimensional invariant ...
    • Geometric quantization of almost toric manifolds 

      Miranda Galcerán, Eva; Presas, Francisco; Barbieri Solha, Romero (2020)
      Article
      Accés obert
      Kostant gave a model for the geometric quantization via the cohomology associated to the sheaf of flat sections of a pre-quantum line bundle. This model is well-adapted for real polarizations given by integrable systems ...
    • Integrable systems on singular symplectic manifolds: from local to global 

      Cardona Aguilar, Robert; Miranda Galcerán, Eva (2020-09)
      Report de recerca
      Accés obert
      In this article we consider integrable systems on manifolds endowed with singular sym-plectic structures of order one. By singular symplectic structures of order one we mean structureswhich are symplectic away from an ...
    • Lower and upper bounds for the splitting of separatrices of the pendulum under a fast quasiperiodic forcing 

      Delshams Valdés, Amadeu; Gelfreich, Vassili; Jorba, Angel; Martínez-Seara Alonso, M. Teresa (1997)
      Article
      Accés obert
      Quasiperiodic perturbations with two frequencies $(1/\varepsilon ,\gamma /\varepsilon )$ of a pendulum are considered, where $\gamma $ is the golden mean number. We study the splitting of the three-dimensional invariant ...
    • Melnikov potential for exact symplectic maps 

      Delshams Valdés, Amadeu; Ramírez Ros, Rafael (1997)
      Article
      Accés obert
      The splitting of separatrices of hyperbolic fixed points for exact symplectic maps of $n$ degrees of freedom is considered. The non-degenerate critical points of a real-valued function (called the Melnikov potential) are ...
    • Microbial individual-based models and sensitivity analyses: local and global methods 

      Ginovart Gisbert, Marta; Prats Soler, Clara; Portell Canal, Xavier (2011)
      Comunicació de congrés
      Accés restringit per política de l'editorial
      A microbial Individual-based Model (IbM) to deal with yeast populations growing in liquid batch cultures has been designed and implemented in a simulator called INDISIM-YEAST. Interesting qualitative results have already ...
    • Motion near the transition to complex instability: some examples 

      Ollé Torner, Mercè; Pacha Andújar, Juan Ramón (1997)
      Article
      Accés obert
      Complex instability is a generic kind of instability in Hamiltonian systems with three degrees of freedom. In this work, some examples of such instability are shown, together with a numerical analysis of the dynamics ...
    • Numerical computation of normal forms around some periodic orbits of the restricted three body problem 

      Jorba, Angel; Villanueva Castelltort, Jordi (1997)
      Article
      Accés obert
      In this paper we introduce a general methodology for computing (numerically) the normal form around a periodic orbit of an autonomous analytic Hamiltonian system. The process follows two steps. First, we expand the ...
    • On quasiperiodic perturbations of elliptic equilibrium points 

      Jorba, Angel; Simó Torres, Carlos (1995)
      Article
      Accés obert
      This work focusses on quasiperiodic time-dependent perturbations of ordinary differential equations near elliptic equilibrium points. This means studying $$ \dot{x}=(A+\varepsilon Q(t,\varepsilon))x+\varepsilon ...
    • On the normal behaviour of partially elliptic lower dimensional tori of hamiltonian systems 

      Jorba, Angel; Villanueva Castelltort, Jordi (1996)
      Article
      Accés obert
      The purpose of this paper is to study the dynamics near a reducible lower dimensional invariant tori of a finite-dimensional autonomous Hamiltonian system with $\ell$ degrees of freedom. We will focus in the case in ...
    • Pseudo-normal form near saddle-center or saddle-focus equilibria 

      Delshams Valdés, Amadeu; Lázaro Ochoa, José Tomás (2003)
      Article
      Accés obert
      In this paper we introduce the pseudo-normal form, which generalizes the notion of normal form around an equilibrium. Its convergence is proved for a general analytic system in a neighborhood of a saddle-center or a ...