The dynamical system generated by the floor function $\lfloor\lambda x\rfloor$

Abstract

We investigate the dynamical system generated by the function $\lfloor\lambda x\rfloor$ defined on $\mathbb R$ and with a parameter $\lambda\in \mathbb R$. For each given $m\in \mathbb N$ we show that there exists a region of values of $\lambda$, where the function has exactly $m$ fixed points (which are non-negative integers), also there is another region for $\lambda$, where there are exactly $m+1$ fixed points (which are non-positive integers). Moreover the full set $\mathbb Z$ of integer numbers is the set of fixed points iff $\lambda=1$. We show that depending on $\lambda$ and on the initial point $x$ the limit of the forward orbit of the dynamical system may be one of the following possibilities: (i) a fixed point, (ii) a two-periodic orbit or (iii) $\pm\infty$.