## Generalized counterexamples to the Seifert conjecture.(English)Zbl 0856.57026

Ann. Math. (2) 143, No. 3, 547-576 (1996); correction ibid. 144, No. 2, 239-268 (1996).
The famous Seifert problem asserts that every dynamical system on the 3-sphere $$S^3$$ with no singular points has a periodic trajectory. The main purpose of this note is to establish that a foliation of any codimension of any manifold can be modified in a real analytic or piecewise-linear fashion so that all minimal sets have codimension 1. The dynamical systems on $$S^3$$ are investigated.
Theorem: The sphere $$S^3$$ has an analytic dynamical system such that all limit sets are 2-dimensional. In particular, it has no circular trajectories.
In PL category, the authors prove the following theorem:
A 1-foliation of a manifold of dimension at least 3 can be modified in a PL fashion so there are no closed leaves but all minimal sets are 1-dimensional. Moreover, if the manifold is closed, then there is an aperiodic PL modification with only one minimal set, and the minimal set is 1-dimensional.
The method: all counterexamples to the Seifert conjecture described here are based on constructions of aperiodic plugs. The exposition is clear and all the fundamental concepts are defined.

### MSC:

 57R30 Foliations in differential topology; geometric theory 57N12 Topology of the Euclidean $$3$$-space and the $$3$$-sphere (MSC2010) 53C12 Foliations (differential geometric aspects)
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