The saga of a fish: from a survival guide to closing lemmas

Sergey Kryzhevich; Eugene Stepanov

doi:10.1016/j.jde.2019.04.010

The saga of a fish: from a survival guide to closing lemmas

Abstrakt

In the paper by D. Burago, S. Ivanov and A. Novikov, “A survival guide for feeble fish”, it has been shown that a fish with limited velocity can reach any point in the (possibly unbounded) ocean provided that the fluid velocity field is incompressible, bounded and has vanishing mean drift. This result extends some known global controllability theorems though being substantially nonconstructive. We give a fish a different recipe of how to survive in a turbulent ocean, and show its relationship to structural stability of dynamical systems by providing a constructive way to change slightly the velocity field to produce conservative (in the sense of not having wandering sets of positive measure) dynamics. In particular, this leads to the extension of C. Pugh’s closing lemma to incompressible vector fields over unbounded domains. The results are based on an extension of the Poincaré recurrence theorem to some σ -finite measures and on specially constructed Newtonian potentials.

Cytowania

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Autorzy (2)

Sergey Kryzhevich dr hab.
- University of Nova Gorica, Slovenia
Eugene Stepanov Prof.
- St. Petersburg Branch of the Steklov Mathematical Institute of the Russian Academy of Sciences, Russia