Periodic orbits of large diameter for circle maps

Lluís Alsedà, Sylvie Ruette

Published 2019-01-06Version 1

Let $f$ be a continuous circle map and let $F$ be a lifting of $f$. In this note we study how the existence of a large orbit for $F$ affects its set of periods. More precisely, we show that, if $F$ is of degree $d\geq 1$ and has a periodic orbit of diameter larger than 1, then $F$ has periodic points of period $n$ for all integers $n\geq 1$, and thus so has $f$. We also give examples showing that this result does not hold when the degree is non positive.