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We derive the modulation equations or Whitham equations for the Camassa– Holm (CH) equation. We show that the modulation equations are hyperbolic and admit bi-Hamiltonian structure. Furthermore they are connected by a reciprocal transformation to the modulation equations of the first negative flow of the Korteweg de Vries (KdV) equation. The reciprocal… (More)

We consider algebraic geometrical properties of the integrable billiard on a quadric Q with elastic impacts along another quadric confocal to Q. These properties are in sharp contrast with those of the ellipsoidal Birkhoff billiards in R n. Namely, generic complex invariant manifolds are not Abelian varieties, and the billiard map is no more algebraic. A… (More)

- Simonetta Abenda
- 2009

We start from a hyperbolic DN hydrodynamic type system of dimension n which possesses Riemann invariants and we settle the necessary conditions on the conservation laws in the reciprocal transformation so that, after such a transformation of the independent variables, one of the metrics associated to the initial system be flat. We prove the following… (More)

We consider hydrodynamic systems which possess a local Hamiltonian structure of Dubrovin-Novikov type. To such a system there are also associated an infinite number of nonlocal Hamiltonian strctures of Mokhov-Ferapontov type. We give necessary and sufficient conditions so that, after a nonlinear transformation of the independent variables, the reciprocal… (More)

- Simonetta Abenda
- 2008

We prove that any real doubly periodic geodesic on an n dimensional ellip-soid with distinct semiaxes and caustic parameters is uniquely associated to a real hyperelliptic tangential cover and that the following density property holds: given a real closed geodesic on the ellipsoid Q = {X 2

- Simonetta Abenda, Pierre Moussa, Andrew H Osbaldestin
- 1997

Using thermodynamical formalism, we set up the perturbative approach for the Hausdorr dimension and the dimension spectrum of the Julia set associated with polynomials close to monomials. We extend previous calculations to a more general case where the perturbation is not constant.

The small dispersion limit of solutions to the Camassa-Holm (CH) equation is characterized by the appearance of a zone of rapid modulated oscillations. An asymptotic description of these oscillations is given, for short times, by the one-phase solution to the CH equation, where the branch points of the corresponding elliptic curve depend on the physical… (More)

- SIMONETTA ABENDA, PETR G. GRINEVICH
- 2009

In our paper we study periodic geodesic motion on multidimensional ellipsoids with elastic impacts along confocal quadrics. We show that the method of isoperiodic deformation is applicable.

- Simonetta Abenda
- 2008

Algebraically closed real geodesics on n-dimensional ellipsoids are dense in the parameter space and related to hyperelliptic tangential coverings * Simonetta Abenda Abstract The closedness condition for real geodesics on n–dimensional ellipsoids is in general transcendental in the parameters (semiaxes of the ellipsoid and constants of motion). We show that… (More)