# Forcing and entropy of strip patterns of quasiperiodic skew products in the cylinder

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## Abstract

© 2015 Elsevier Inc. We extend the results and techniques from [7] to study the combinatorial dynamics (forcing) and entropy of quasiperiodically forced skew-products on the cylinder. For these maps we prove that a cyclic permutation τ forces a cyclic permutation ν as interval patterns if and only if τ forces ν as cylinder patterns. This result gives as a corollary the Sharkovskiĭ Theorem for quasiperiodically forced skew-products on the cylinder proved in [7]. Next, the notion of s-horseshoe is defined for quasiperiodically forced skew-products on the cylinder and it is proved, as in the interval case, that if a quasiperiodically forced skew-product on the cylinder has an s-horseshoe then its topological entropy is larger than or equals to log(s). Finally, if a quasiperiodically forced skew-product on the cylinder has a periodic orbit with pattern τ, then h(F)≥h(f<inf>τ</inf>), where f<inf>τ</inf> denotes the connect-the-dots interval map over a periodic orbit with pattern τ. This implies that if the period of τ is 2<sup>n</sup>q with n≥0 and q≥1 odd, then h(F)≥log(λ<inf>q</inf>)/2<sup>n</sup>, where λ<inf>1</inf>=1 and, for each q≥3, λ<inf>q</inf> is the largest root of the polynomial x<sup>q</sup>-2x<sup>q-2</sup>-1. Moreover, for every m=2<sup>n</sup>q with n≥0 and q≥1 odd, there exists a quasiperiodically forced skew-product on the cylinder F<inf>m</inf> with a periodic orbit of period m such that h(Fm)=log(λ<inf>q</inf>)/2<sup>n</sup>. This extends the analogous result for interval maps to quasiperiodically forced skew-products on the cylinder.
Original language English 542-561 Journal of Mathematical Analysis and Applications 429 1 https://doi.org/10.1016/j.jmaa.2015.03.038 Published - 1 Jan 2015

## Keywords

• Combinatorial dynamics
• Forcing entropy
• Irrational rotation
• Quasiperiodically forced systems on the cylinder