Ara es mostren els items 16-30 de 30

    • Homoclinic billiard orbits inside symmetrically perturbed ellipsoids 

      Delshams Valdés, Amadeu; Fedorov, Yuri; Ramírez Ros, Rafael (2000)
      Article
      Accés obert
      The billiard motion inside an ellipsoid of ${\bf R}^{3}$ is completely integrable. If the ellipsoid is not of revolution, there are many orbits bi-asymptotic to its major axis. The set of bi-asymptotic orbits is described ...
    • Homoclinic orbits of twist maps and billiards 

      Delshams Valdés, Amadeu; Ramírez Ros, Rafael (1997)
      Article
      Accés obert
      The splitting of separatrices for hyperbolic fixed points of twist maps with $d$ degrees of freedom is studied through a real-valued function, called the Melnikov potential. Its non-degenerate critical points are associated ...
    • 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 ...
    • Modelització amb sistemes d'EDOs lineals 

      Ramírez Ros, Rafael (2019-04-10)
      Audiovisual
      Accés obert
    • On Birkhoff's conjecture about convex billiards 

      Delshams Valdés, Amadeu; Ramírez Ros, Rafael (1995)
      Article
      Accés obert
      Birkhoff conjectured that the elliptic billiard was the only integrable convex billiard. Here we prove a local version of this conjecture: any non-trivial symmetric entire perturbation of an elliptic billiard is non-integrable.
    • On the length and area spectrum of analytic convex domains 

      Martín, Pau; Ramírez Ros, Rafael; Tamarit Sariol, Anna (2016-01)
      Article
      Accés obert
      Area-preserving twist maps have at least two different (p, q)-periodic orbits and every (p, q)-periodic orbit has its (p, q)-periodic action for suitable couples (p, q). We establish an exponentially small upper bound for ...
    • Persistence of homoclinic orbits for billiards and twist maps 

      Bolotin, S.; Delshams Valdés, Amadeu; Ramírez Ros, Rafael (2003)
      Article
      Accés obert
      We consider the billiard motion inside a C2-small perturbation of a ndimensional ellipsoid Q with a unique major axis. The diameter of the ellipsoid Q is a hyperbolic two-periodic trajectory whose stable and unstable ...
    • Poincaré-Melnikov-Arnold method for analytic planar maps 

      Delshams Valdés, Amadeu; Ramírez Ros, Rafael (1995)
      Article
      Accés obert
      The Poincare-Melnikov-Arnold method for planar maps gives rise to a Melnikov function defined by an infinite and (a priori) analytically uncomputable sum. Under an assumption of meromorphicity, residues theory can be ...
    • Poincaré-Melnikov-Arnold method for twist maps 

      Delshams Valdés, Amadeu; Ramírez Ros, Rafael (1997)
      Article
      Accés obert
      The Poincar\'e--Melnikov--Arnold method is the standard tool for detecting splitting of invariant manifolds for systems of ordinary differential equations close to ``integrable'' ones with associated separatrices. This ...
    • Singular separatrix splitting and Melnikov method: An experimental study 

      Delshams Valdés, Amadeu; Ramírez Ros, Rafael (1998)
      Article
      Accés obert
      We consider families of analytic area-preserving maps depending on two pa- rameters: the perturbation strength E and the characteristic exponent h of the origin. For E=0, these maps are integrable with a separatrix to ...
    • Singular separatrix splitting and the Poincare-Melnikov method for area preserving maps 

      Delshams Valdés, Amadeu; Ramírez Ros, Rafael (1999)
      Article
      Accés obert
      The splitting of separatrices of area preserving maps close to the identity is one of the most paradigmatic examples of an exponentially small or singular phenomenon. The intrinsic small parameter is the characteristic ...
    • Singular splitting of separatrices for the perturbed McMillan map 

      Delshams Valdés, Amadeu; Ramírez Ros, Rafael (1998)
      Article
      Accés obert
    • Splitting of separatrices in Hamiltonian systems and symplectic maps 

      Delshams Valdés, Amadeu; Martínez-Seara Alonso, M. Teresa; Ramírez Ros, Rafael (1997)
      Article
      Accés obert
      Poincar\'e, Melnikov and Arnol'd introduced the standard method for measuring the splitting of separatrices of Hamiltonian systems. It is based on the study of the zeros of the so-called Melnikov integral, a vectorial ...
    • Stability of the phase motion in race-track microtrons 

      Kubyshin, Yu A.; Larreal Barreto, Oswaldo; Ramírez Ros, Rafael; Martínez-Seara Alonso, M. Teresa (2017-06-15)
      Article
      Accés obert
      We model the phase oscillations of electrons in race-track microtrons by means of an area preserving map with a fixed point at the origin, which represents the synchronous trajectory of a reference particle in the beam. ...
    • The frequency map for billiards inside ellipsoids 

      Ramírez Ros, Rafael; Sánchez Casas, José Pablo (2010-04)
      Report de recerca
      Accés obert
      The billiard motion inside an ellipsoid Q Rn+1 is completely integrable. Its phase space is a symplectic manifold of dimension 2n, which is mostly foliated with Liouville tori of dimension n. The motion on each Liouville ...