Forward triplets and topological entropy on trees
We provide a new and very simple criterion of positive topological entropy for tree maps. We prove that a tree map f has positive entropy if and only if some iterate fk has a periodic orbit with three aligned points consecutive in time, that is, a triplet (a,b,c) such that fk(a)=b, fk(b)=c and b bel...
| Authors: | , , |
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| Format: | article |
| Publication Date: | 2022 |
| Country: | España |
| Institution: | Universitat Autònoma de Barcelona |
| Repository: | Dipòsit Digital de Documents de la UAB |
| Language: | English |
| OAI Identifier: | oai:ddd.uab.cat:257126 |
| Online Access: | https://ddd.uab.cat/record/257126 https://dx.doi.org/urn:doi:10.3934/dcds.2021131 |
| Access Level: | Open access |
| Keyword: | Tree maps Periodic patterns Topological entropy |
| Summary: | We provide a new and very simple criterion of positive topological entropy for tree maps. We prove that a tree map f has positive entropy if and only if some iterate fk has a periodic orbit with three aligned points consecutive in time, that is, a triplet (a,b,c) such that fk(a)=b, fk(b)=c and b belongs to the interior of the unique interval connecting a and c (a forward triplet of fk). We also prove a new criterion of entropy zero for simplicial n-periodic patterns P based on the non existence of forward triplets of fk for any 1≤k<n inside P. Finally, we study the set Xn of all n-periodic patterns P that have a forward triplet inside P. For any n, we define a pattern that attains the minimum entropy in Xn and prove that this entropy is the unique real root in (1,∞) of the polynomial xn-2x-1. |
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