@article {2007,
title = {On feedback classification of control-affine systems with one and two-dimensional inputs},
journal = {SIAM J. Control Optim. 46 (2007) 1431-1460},
number = {arXiv.org;math/050231v2},
year = {2007},
abstract = {The paper is devoted to the local classification of generic control-affine systems on an n-dimensional manifold with scalar input for any n>3 or with two inputs for n=4 and n=5, up to state-feedback transformations, preserving the affine structure. First using the Poincare series of moduli numbers we introduce the intrinsic numbers of functional moduli of each prescribed number of variables on which a classification problem depends. In order to classify affine systems with scalar input we associate with such a system the canonical frame by normalizing some structural functions in a commutative relation of the vector fields, which define our control system. Then, using this canonical frame, we introduce the canonical coordinates and find a complete system of state-feedback invariants of the system. It also gives automatically the micro-local (i.e. local in state-input space) classification of the generic non-affine n-dimensional control system with scalar input for n>2. Further we show how the problem of feedback-equivalence of affine systems with two-dimensional input in state space of dimensions 4 and 5 can be reduced to the same problem for affine systems with scalar input. In order to make this reduction we distinguish the subsystem of our control system, consisting of the directions of all extremals in dimension 4 and all abnormal extremals in dimension 5 of the time optimal problem, defined by the original control system. In each classification problem under consideration we find the intrinsic numbers of functional moduli of each prescribed number of variables according to its Poincare series.},
doi = {10.1137/050623711},
url = {http://hdl.handle.net/1963/2186},
author = {Andrei A. Agrachev and Igor Zelenko}
}
@article {2007,
title = {On finite-dimensional projections of distributions for solutions of randomly forced PDE\\\'s},
journal = {Ann. Inst. Henri Poincare-Prob. Stat. 43 (2007) 399-415},
number = {arXiv.org;math/0603295},
year = {2007},
abstract = {The paper is devoted to studying the image of probability measures on a Hilbert space under finite-dimensional analytic maps. We establish sufficient conditions under which the image of a measure has a density with respect to the Lebesgue measure and continuously depends on the map. The results obtained are applied to the 2D Navier-Stokes equations perturbed by various random forces of low dimension.},
doi = {10.1016/j.anihpb.2006.06.001},
url = {http://hdl.handle.net/1963/2012},
author = {Andrei A. Agrachev and Sergei Kuksin and Andrey Sarychev and Armen Shirikyan}
}