LEGA , Elena

Comet 67P/Churyumov-Gerasimenko is the target of the Rosetta mission. On the base of backward numerical integrations of a large set of fictitious comets whose initial conditions are obtained from small variations of the orbital parameters of 67P, and the analysis of suitable chaos indicators, we detect the phase–space structure of the past...

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In the last decades finite time chaos indicators have been used to compute the phase-portraits of complex dynamics as well as the center, stable and unstable manifolds originating at the partially hyperbolic equilibria, and the Lagrangian Coherent Structures of aperiodic flows. While the definition of most chaos indicators is clearly inspired...

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The circular restricted three-body problem has five relative equilibria L1 , L2 , ..., L5. Theinvariant stable-unstable manifolds of the center manifolds originating at the partially hy-perbolic equilibria L1 ,L2 have been identified as the separatrices for the motions which transit between the regions of the phase–space which are internal or...

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We detect and measure diffusion along resonances in a discrete symplectic map for different values of the coupling parameter. Qualitatively and quantitatively the results are very similar to those obtained for a quasi-integrable Hamiltonian system, i.e. in agreement with Nekhoroshev predictions, although the discrete mapping does not fulfill...

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Using numerical methods we study the hyperbolic manifolds in a model of a priori unstable dynamical system. We compare the numerically computed manifolds with their analytic expression obtained with the Melnikov approximation. We find that, at small values of the perturbing parameter, the topology of the numerically computed stable and unstable...

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Different numerical methods, for the computation of frequency versus initial conditions in the four-dimensional standard mapping, are proposed. The first method relies on the analytic properties of invariant rotational tori. A purely numerical technique was derived from an extension of a method suggested by M. Hénon for the two-dimensional...

We investigate numerically the stable and unstable manifolds of the hyperbolic manifolds of the phase space related to the resonances of quasi-integrable systems in the regime of validity of the Nekhoroshev and KAM theorems. Using a model of weakly interacting resonances we explain the qualitative features of these manifolds characterized by...