Bifurcation at Complex Instability

The properties of motion close to the transition of a stable family of periodic orbits to complex instability is investigated with two symplectic 4D mappings, natural extensions of the standard mapping. As for the other types of instabilities new families of periodic orbits may bifurcate at the transition; but, more generally, families of {\sl isolated invariant curves} bifurcate, similar to but distinct from a Hopf bifurcation. The evolution of the stable invariant curves and their bifurcations are described.Comment: 5 pages, self-unpacking uuencoded compressed Postscript, Contribution at the NATO ASI Conference on "Hamiltonian Systems with Three or More Degrees of Freedom, Barcelona, Spain, June 19-30, 199

Invariant curves near Hamiltonian-Hopf bifurcations of 4D symplectic maps

In this paper we give a numerical description of the neighbourhood of a fixed point of a symplectic map undergoing a transition from linear stability to complex instability, i.e., the so called Hamiltonian-Hopf bifurcation. We have considered both the direct and inverse cases. The study is based on the numerical computation of the Lyapunov families of invariant curves near the fixed point. We show how these families, jointly with their invariant manifolds and the invariant manifolds of the fixed point organise the phase space around the bifurcation

Invariant manifolds of L_3 and horseshoe motion in the restricted three-body problem

In this paper, we consider horseshoe motion in the planar restricted three-body problem. On one hand, we deal with the families of horseshoe periodic orbits (which surround three equilibrium points called L3, L4 and L5), when the mass parameter µ is positive and small; we describe the structure of such families from the two-body problem (µ = 0). On the other hand, the region of existence of horseshoe periodic orbits for any value of µ ∈ (0, 1/2] implies the understanding of the behaviour of the invariant manifolds of L3. So, a systematic analysis of such manifolds is carried out. As well the implications on the number of homoclinic connections to L3, and on the simple infinite and double infinite period homoclinic phenomena are also analysed. Finally, the relationship between the horseshoe homoclinic orbits and the horseshoe periodic orbits are considered in detail

Hopf bifurcation for the hydrogen atom in a circularly polarized microwave field

We consider the Rydberg electron in a circularly polarized microwave field, whose dynamics is described by a Hamiltonian depending on one parameter, K¿>¿0. The corresponding Hamiltonian system of ODE has two equilibrium points L1 (unstable for all K and energy value h(L1)) and L2 (a center for K¿¿Kcrit, with energy value h(L2)). We study the Hamiltonian-Hopf bifurcation phenomena that take place for K close to Kcrit around L2. First, a local analysis based on the computation of the integrable normal form up to a finite order is carried out and the steps for the computation of this (resonant) normal form are explained in a constructive manner. The analysis of the normal form obtained allows: to claim the type of the Hopf bifurcation –supercritical–; to study the local behavior of the electron in a neighborhood of the equilibrium L2 for the original non integrable Hamiltonian (as a perturbative approach from the integrable normal form); to obtain (approximations for) the parametrizations of the relevant invariant objects that take place due to the bifurcation (periodic orbits and invariant manifolds of L2). We compute numerically such objects and analyse not only the local picture of the dynamics close to L2, but also a global description of the dynamics and the effect of the Hopf bifurcation as well as other objects that organize the dynamics are discussed. We conclude that, for K close to Kcrit and the energy level h(L2), the Hopf bifurcation has essentially no effect on the dynamics from a physical point of view. However, for bigger values of K¿>¿Kcrit, the Hopf bifurcation has a dramatic effect: different kind of orbits coexist, mostly chaotic. Such orbits provide a ionization mechanism with several passages far from and close to L2 before ionizing. Surprisingly enough, also robust confinement regions (where the electron remains confined for ever), exist in the middle of chaotic areasPeer ReviewedPostprint (published version

Motion near the transition to complex instability: some examples

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 close to the transition from stability to comlex instability for a family of periodic orbits

Pseudo-heteroclinic connections between bicircular restricted four-body problems

In this paper, we show a mechanism to explain transport from the outer to the inner Solar system. Such a mechanism is based on dynamical systems theory. More concretely, we consider a sequence of uncoupled bicircular restricted four-body problems –BR4BP –(involving the Sun, Jupiter, a planet and an infinitesimal mass), being the planet Neptune, Uranus and Saturn. For each BR4BP, we compute the dynamical substitutes of the collinear equilibrium points of the corresponding restricted three-body problem (Sun, planet and infinitesimal mass), which become periodic orbits. These periodic orbits are unstable, and the role that their invariant manifolds play in relation with transport from exterior planets to the inner ones is discussed.Peer ReviewedPostprint (published version

Unint esforços per avançar en agricultura sostenible

Investigadores del Departament de Biologia Animal, de Biologia Vegetal i d'Ecologia de la UAB participen al projecte PALVIP (Protecció Alternativa de les Produccions Vegetals Interregionals dels Pirineus), una iniciativa per desenvolupar bioplaguicides adaptats als cultius mediterranis i afavorir una agricultura sostenible a Catalunya i el Rosselló. El projecte suposa la creació d'una xarxa de recerca per fer front als reptes de la producció agrícola i els productes de biocontrol al territori.Investigadoras del Departamento de Biología Animal, Biología Vegetal y Ecología de la UAB participan en el proyecto PALVIP (Protección Alternativa de las Producciones Vegetales Interregionales de los Pirineos), una iniciativa para desarrollar bioplaguicidas adaptados a los cultivos mediterráneos y favorecer la agricultura sostenible en Cataluña y el Rosellón, que supone la creación de una red de investigación para hacer frente a los retos agrícolas y los productos de biocontrol en el territorio.UAB Plant Biology researchers participate in the PALVIP project (Alternative Protection of Interregional Plant Productions of the Pyrenees), to develop biocontrol products adapted to Mediterranean crops and promote sustainable agriculture in Catalonia and Roussillon. The project involves the creation of a cross-border research network to meet the challenges of the agricultural production and biocontrol products in the territory

KAM aspects of the quasi-periodic Hamiltonian Hopf bifurcation: summary of results

In this work we consider a 1:-1 non semi-simple resonant periodic orbit of a three-degrees of freedom real analytic Hamiltonian system. From the formal analysis of the normal form, it is proved the branching off a two-parameter family of two-dimensional invariant tori of the normalised system, whose normal behaviour depends intrinsically on the coefficients of its low-order terms. Thus, only elliptic or elliptic together with parabolic and hyperbolic tori may detach form the resonant periodic orbit. Both patterns are mentioned in the literature as the direct and, respectively, inverse quasiperiodic Hopf bifurcation. In this report we focus on the direct case, which has many applications in several fields of science. Thus, we present here a summary of the results, obtained in the framework of KAM theory, concerning the persistence of most of the (normally) elliptic tori of the normal form, when the whole Hamiltonian is taken into account, and to give a very precise characterisation of the parameters labelling them, which can be selected with a very clear dynamical meaning. These results include sharp quantitative estimates on the “density” of surviving tori, when the distance to the resonant periodic orbit goes to zero, and state that the 4-dimensional Cantor manifold holding these tori admits a Whitney-C^\infty extension. In addition, an application to the Circular Spatial Three-Body Problem (CSRTBP) is reviewed.Peer Reviewe