8,627 research outputs found
The geometry of optimal control problems on some six dimensional lie groups
This paper examines optimal solutions of control systems with drift defined on the orthonormal frame bundle of particular Riemannian manifolds of constant curvature. The manifolds considered here are the space forms Euclidean space E3 , the spheres S3 and the hyperboloids H3 with the corresponding frame bundles equal to the Euclidean group of motions SE(3), the rotation group SO(4) and the Lorentz group SO(1,3). The optimal controls of these systems are solved explicitly in terms of elliptic functions. In this paper, a geometric interpretation of the extremal solutions is given with particular emphasis to a singularity in the explicit solutions. Using a reduced form of the Casimir functions the geometry of these solutions are illustrated
Non-minimality of corners in subriemannian geometry
We give a short solution to one of the main open problems in subriemannian
geometry. Namely, we prove that length minimizers do not have corner-type
singularities. With this result we solve Problem II of Agrachev's list, and
provide the first general result toward the 30-year-old open problem of
regularity of subriemannian geodesics.Comment: 11 pages, final versio
Singular solutions of a modified two-component Camassa-Holm equation
The Camassa-Holm equation (CH) is a well known integrable equation describing
the velocity dynamics of shallow water waves. This equation exhibits
spontaneous emergence of singular solutions (peakons) from smooth initial
conditions. The CH equation has been recently extended to a two-component
integrable system (CH2), which includes both velocity and density variables in
the dynamics. Although possessing peakon solutions in the velocity, the CH2
equation does not admit singular solutions in the density profile. We modify
the CH2 system to allow dependence on average density as well as pointwise
density. The modified CH2 system (MCH2) does admit peakon solutions in velocity
and average density. We analytically identify the steepening mechanism that
allows the singular solutions to emerge from smooth spatially-confined initial
data. Numerical results for MCH2 are given and compared with the pure CH2 case.
These numerics show that the modification in MCH2 to introduce average density
has little short-time effect on the emergent dynamical properties. However, an
analytical and numerical study of pairwise peakon interactions for MCH2 shows a
new asymptotic feature. Namely, besides the expected soliton scattering
behavior seen in overtaking and head-on peakon collisions, MCH2 also allows the
phase shift of the peakon collision to diverge in certain parameter regimes.Comment: 25 pages, 11 figure
On Regularity of Abnormal Subriemannian Geodesics
We prove the smoothness of abnormal minimizers of subriemannian manifolds of
step 3 with a nilpotent basis. We prove that rank 2 Carnot groups of step 4
admit no strictly abnormal minimizers. For any subriemannian manifolds of step
less than 7, we show all abnormal minimizers have no corner type singularities,
which partly generalize the main result of Leonardi-Monti.Comment: This paper has been withdrawn by the author due to a crucial
computation error in (F_t^1)_sta
Examples of integrable sub-Riemannian geodesic flows
Motivated by a paper of Bolsinov and Taimanov DG/9911193 we consider
non-holonomic situation and exhibit examples of sub-Riemannian metrics with
integrable geodesic flows and positive topological entropy. Moreover the
Riemannian examples are obtained as "holonomization" of sub-Riemannian ones. A
feature of non-holonomic situation is non-compactness of the phase space.
We also exhibit a Liouvulle-integrable Hamiltonian system with topological
entropy of all integrals positive.Comment: 21 pages; Answer to the self-posed question is added: Is it possible
to construct Liouville-integrable Hamiltonian system with positive
topological entropies of all integrals? Yes and we present an exampl
Nonisotropic 3-level Quantum Systems: Complete Solutions for Minimum Time and Minimum Energy
We apply techniques of subriemannian geometry on Lie groups and of optimal
synthesis on 2-D manifolds to the population transfer problem in a three-level
quantum system driven by two laser pulses, of arbitrary shape and frequency. In
the rotating wave approximation, we consider a nonisotropic model i.e. a model
in which the two coupling constants of the lasers are different. The aim is to
induce transitions from the first to the third level, minimizing 1) the time of
the transition (with bounded laser amplitudes),
2) the energy of lasers (with fixed final time). After reducing the problem
to real variables, for the purpose 1) we develop a theory of time optimal
syntheses for distributional problem on 2-D-manifolds, while for the purpose 2)
we use techniques of subriemannian geometry on 3-D Lie groups. The complete
optimal syntheses are computed.Comment: 29 pages, 6 figure
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