On the number of parameters $c$ for which the point $x=0$ is a superstable periodic point of $f_c(x)=1-c{x}^2$

Abstract

Let $f_c(x)=1-c{x}^2$ be a one-parameter family of real continuous maps with parameter $c\ge 0$. For every positive integer $n$, let $N_n$ denote the number of parameters $c$ such that the point $x=0$ is a (superstable) periodic point of $f_c(x)$ whose least period divides $n$ (in particular, $f_c^n(0)=0$). In this note, we find a recursive way to depict how {\it some} of these parameters $c$ appear in the interval $[0,2]$ and show that ${\mathrm{liminf}}_{n\to \infty }(\log N_n)/n\ge \log 2$ and this result is generalized to a class of one-parameter families of continuous real-valued maps that includes the family $f_c(x)=1-c{x}^2$.

arXiv comment7 pages, 1 figure