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Entropy of snakes and the restricted variational principle. (English) Zbl 0784.54025
The paper deals with the entropy of an oriented pattern. An oriented pattern is an equivalence class of a relation on the set of cycles (periodic orbits) of continuous maps of an interval into itself. The entropy of an oriented pattern is the smallest topological entropy of a map exhibiting this pattern.
The sequence of topological entropies $$h(O_ n)$$ of the oriented patterns $$O_ n$$ of period $$n$$ approaches a limit value. In this paper is described a method for finding limit entropy in terms of the entropy of a graph $$G$$ with labels which generates the graph of the oriented pattern. The limit is obtained in the form of a variational principle, the supremum of metric entropies is taken over the set of all invariant ergodic probabilistic measures on the subshift of finite type $$\Sigma\subset \Delta^ \mathbb{Z}$$ ($$\Delta$$ is the set of arrows of the graph) for which $$\int f d\mu= 0$$, $$f$$ being a function $$f: \Sigma\to\mathbb{Z}$$ associated to the problem. In the case when the graph $$G$$ exhibits a kind of symmetry the method gives direct results.
Finally are given applications to snakes which are oriented patterns $$O_ n$$ $$(1,3,5,\dots,n,n-1,\dots,4,2)$$ if $$n$$ is odd, and $$(1,3,5,\dots,n-1,n,n-2,\dots,4,2)$$ if $$n$$ is even, and to topological entropy of countable chains.
##### MSC:
 54C70 Entropy in general topology 37A99 Ergodic theory
##### Keywords:
oriented pattern; topological entropy
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##### References:
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