Ara es mostren els items 1-20 de 20

• #### A geometric approach to the existence of orbits with unbounded energy in generic periodic perturbations by a potential of generic geodesic flows of T<sup>2</sup> ﻿

(1999)
Article
Accés obert
We give a proof based in geometric perturbation theory of a result proved by J.N. Mather using variational methods. Namely, the existence of orbits with unbounded energy in perturbations of a generic geodesic flow in T^2 ...
• #### A geometric mechanism for diffusion in Hamiltonian systems overcoming the large gap problem: heuristics and rigorous verification on a model. ﻿

(2003)
Article
Accés obert
We introduce a geometric mechanism for di?usion in a priori unstable nearly integrable dynamical systems. It is based on the observation that resonances, besides destroying the primary KAM tori, create secondary tori and ...
• #### A geometric mechanism for diffusion in Hamiltonian systems overcoming the large gap problem: Announcement of results ﻿

(2003)
Article
Accés obert
We present a geometric mechanism for diﬀusion in Hamiltonian systems. We also present tools that allow to verify it in a concrete model. In particular, we verify it in a system which presents the large gap problem.
• #### A smooth center manifold theorem which applies to some III-posed partial differential equations with unbounded nonlinearities ﻿

(2009)
Article
Accés restringit per política de l'editorial
We prove the existence of a smooth center manifold for several partial differential equations, including ill posed equations with unbounded nonlinearities. We also prove smooth dependence on parameters with respect to ...
• #### Computation of limit cycles and their isochrons: Fast algorithms and their convergence ﻿

(2013)
Article
Accés restringit per política de l'editorial
We present efficient algorithms to compute limit cycles and their isochrons (i.e., the sets of points with the same asymptotic phase) for planar vector fields. We formulate a functional equation for the parameterization ...
• #### Dynamical systems on lattices with decaying interaction I: A functional analysis framework ﻿

(2011-03-15)
Article
Accés restringit per política de l'editorial
We consider weakly coupled map lattices with a decaying interaction. That is, we consider systems which consist of a phase space at every site such that the dynamics at a site is little affected by the dynamics at far ...
• #### Dynamical systems on lattices with decaying interaction II: Hyperbolic sets and their invariant manifolds ﻿

(2011-03-15)
Article
Accés restringit per política de l'editorial
This is the second part of the work devoted to the study of maps with decay in lattices. Here we apply the general theory developed in Fontich et al. (2011) to the study of hyperbolic sets. In particular, we establish that ...
• #### Geometric properties of the scattering map of a normally hyperbolic invariant manifold ﻿

(Elsevier, 2008)
Article
Accés obert
Given a normally hyperbolic invariant manifold Λ for a map f , whose stable and unstable invariant manifolds intersect transversally, we consider its associated scattering map. That is, the map that, given an asymptotic ...
• #### Geometric properties of the scattering map of a normally hyperbolic invariant manifold ﻿

(2006-10-10)
Article
Accés obert
Given a normally hyperbolic invariant manifold $\Lambda$ for a map $f$, whose stable and unstable invariant manifolds intersect transversally, we consider its associated scattering map. That is, the map that, given an ...
• #### Instability of high dimensional Hamiltonian systems: Multiple resonances do not impede diffusion ﻿

(2016-05-14)
Article
Accés obert
We consider models given by Hamiltonians of the form View the MathML sourceH(I,f,p,q,t;e)=h(I)+¿j=1n±(12pj2+Vj(qj))+eQ(I,f,p,q,t;e) Turn MathJax on where I¿I¿Rd,f¿TdI¿I¿Rd,f¿Td, p,q¿Rnp,q¿Rn, t¿T1t¿T1. These are higher ...
• #### KAM theory and a partial justification of Greene's criterion for non-twist maps ﻿

(1999)
Article
Accés obert
We consider perturbations of integrable area preserving non twist maps of the annulus those are maps in which the twist condition changes sign These maps appear in a variety of applications notably transport in atmospheric ...
• #### KAM Theory without action--angle variables ﻿

(2003)
Article
Accés obert
Given a torus approximately invariant under a symplectic map, we find sufficient conditions for the existence of a true invariant torus close to the given one. We do not assume either that we are working on action-angle ...
• #### A la recerca de l'estabilitat efectiva dels asteroids trojans : algunes idees constructives de tècniques KAM sense ssar coordenades acció-angle ﻿

(2000)
Text en actes de congrés
Accés obert
Xerrada pel Seminari de Sistemes Dinamics UB-UPC. Barcelona, dimecres 19 de gener de 2000. Els trojans son una familia d'asteroids amb orbites situades no molt lluny del punt $L_5$ del sistema Sol-Jupiter. Si integrem ...
• #### Lindstedt series for lower dimensional tori ﻿

(1995)
Article
Accés obert
We consider the existence and effective computation of low-dimensional (less independent frequencies than degrees of freedom) invariant tori of a near-integrable system. Lindstedt method is a systematic procedure to compute ...
• #### Orbits of unbounded energy in quasi-periodic perturbations of geodesic flows ﻿

(2003)
Article
Accés obert
We show that certain mechanical systems, including a geodesic °ow in any dimension plus a quasi-periodic perturbation by a potential, have orbits of unbounded energy. The assumptions we make in the case of geodesic °ows ...
• #### Teoria Kam Sin Coordenadas Accion-Angulo ﻿

(2001)
Article
Accés obert
The classical KAM methods, strongly supported on the use of canonical trans- formations in the action-angle context, are not effcient to be applied to a wide range of systems in which the Hamiltonian is known (for instance) ...
• #### The parameterization method for invariant manifolds I: manifolds associated to non-resonant subspaces ﻿

(2002)
Article
Accés obert
We introduce a method to prove existence of invariant manifolds and, at the same time to find simple polynomial maps which are conjugated to the dynamics on them. As a first application, we consider the dynamical system ...
• #### The parameterization method for invariant manifolds II: regularity with respect to parameters ﻿

(2002)
Article
Accés obert
We study the regularity with respect to parameters of the invariant manifolds associated to non-resonant subspaces obtained in the previous article [CFdlL00].
• #### The parameterization method for invariant manifolds III: overview and applications ﻿

(2003)
Article
Accés obert
We describe a method to establish existence and regularity of invariant manifolds and, at the same time to find simple maps which are conjugated to the dynamics on them. The method establishes several invariant manifold ...

(1999)
Article
Accés obert