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Transactions of the American Mathematical Society

Published by the American Mathematical Society since 1900, Transactions of the American Mathematical Society is devoted to longer research articles in all areas of pure and applied mathematics.

ISSN 1088-6850 (online) ISSN 0002-9947 (print)

The 2020 MCQ for Transactions of the American Mathematical Society is 1.48.

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The entropy of $C^1$-diffeomorphisms without a dominated splitting
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by Jérôme Buzzi, Sylvain Crovisier and Todd Fisher PDF
Trans. Amer. Math. Soc. 370 (2018), 6685-6734 Request permission

Abstract:

A classical construction due to Newhouse creates horseshoes from hyperbolic periodic orbits with large period and weak domination through local $C^1$-perturbations. Our main theorem shows that when one works in the $C^1$-topology, the entropy of such horseshoes can be made arbitrarily close to an upper bound following from Ruelle’s inequality, i.e., the sum of the positive Lyapunov exponents (or the same for the inverse diffeomorphism, whichever is smaller).

This optimal entropy creation yields a number of consequences for $C^1$-generic diffeomorphisms, especially in the absence of a dominated splitting. For instance, in the conservative settings, we find formulas for the topological entropy, deduce that the topological entropy is continuous but not locally constant at the generic diffeomorphism, and prove that these generic diffeomorphisms have no measure of maximum entropy. In the dissipative setting, we show the locally generic existence of infinitely many homoclinic classes with entropy bounded away from zero.

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Additional Information
  • Jérôme Buzzi
  • Affiliation: Laboratoire de Mathématiques d’Orsay, CNRS - UMR 8628, Université Paris-Sud 11, 91405 Orsay, France
  • Email: jerome.buzzi@math.u-psud.fr
  • Sylvain Crovisier
  • Affiliation: Laboratoire de Mathématiques d’Orsay, CNRS - UMR 8628, Université Paris-Sud 11, 91405 Orsay, France
  • MR Author ID: 691227
  • Email: sylvain.crovisier@math.u-psud.fr
  • Todd Fisher
  • Affiliation: Department of Mathematics, Brigham Young University, Provo, Utah 84602
  • MR Author ID: 681585
  • Email: tfisher@math.byu.edu
  • Received by editor(s): December 28, 2016
  • Published electronically: March 20, 2018
  • Additional Notes: The second author was partially supported by the ERC project 692925 NUHGD
    The third author was supported by Simons Foundation grant #239708.
  • © Copyright 2018 American Mathematical Society
  • Journal: Trans. Amer. Math. Soc. 370 (2018), 6685-6734
  • MSC (2010): Primary 37C15; Secondary 37B40, 37D05, 37D30
  • DOI: https://doi.org/10.1090/tran/7380
  • MathSciNet review: 3814345