In mathematics, a recurrent point for a function f is a point that is in its own limit set by f. Any neighborhood containing the recurrent point will also contain (a countable number of) iterates of it as well.

Definition

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Let   be a Hausdorff space and   a function. A point   is said to be recurrent (for  ) if  , i.e. if   belongs to its  -limit set. This means that for each neighborhood   of   there exists   such that  .[1]

The set of recurrent points of   is often denoted   and is called the recurrent set of  . Its closure is called the Birkhoff center of  ,[2] and appears in the work of George David Birkhoff on dynamical systems.[3][4]

Every recurrent point is a nonwandering point,[1] hence if   is a homeomorphism and   is compact, then   is an invariant subset of the non-wandering set of   (and may be a proper subset).

References

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  1. ^ a b Irwin, M. C. (2001), Smooth dynamical systems, Advanced Series in Nonlinear Dynamics, vol. 17, World Scientific Publishing Co., Inc., River Edge, NJ, p. 47, doi:10.1142/9789812810120, ISBN 981-02-4599-8, MR 1867353.
  2. ^ Hart, Klaas Pieter; Nagata, Jun-iti; Vaughan, Jerry E. (2004), Encyclopedia of general topology, Elsevier, p. 390, ISBN 0-444-50355-2, MR 2049453.
  3. ^ Coven, Ethan M.; Hedlund, G. A. (1980), "  for maps of the interval", Proceedings of the American Mathematical Society, 79 (2): 316–318, doi:10.1090/S0002-9939-1980-0565362-0, JSTOR 2043258, MR 0565362.
  4. ^ Birkhoff, G. D. (1927), "Chapter 7", Dynamical Systems, Amer. Math. Soc. Colloq. Publ., vol. 9, Providence, R. I.: American Mathematical Society. As cited by Coven & Hedlund (1980).


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