Let $ℱ=\{F^v{𝕊}^1\to {𝕊}^1,v\in V\}$ be a disjoint iteration group on the unit circle ${𝕊}^1$, that is a family of homeomorphisms such that $F^{v_1}\circ F^{v_2}=F^{v_1+v_2}$ for $v_1$, $v_2\in V$ and each $F^v$ either is the identity mapping or has no fixed point ($(V,+)$ is a $2$-divisible nontrivial Abelian group). Denote by $L_{ℱ}$ the set of all cluster points of $\{F^v\left(z\right)$, $v\in V\}$ for $z\in {𝕊}^1$. In this paper we give a general construction of disjoint iteration groups for which $\varnothing \ne L_{ℱ}\ne {𝕊}^1$.

Let $\mu$ be a probability measure on $[0,1]$ which is invariant and ergodic for $T_a\left(x\right)=ax\mathrm{𝚖𝚘𝚍}1$, and $0<\mathrm{𝚍𝚒𝚖}\mu <1$. Let $f$ be a local diffeomorphism on some open set. We show that if $E\subseteq ℝ$ and $\left(f\mu \right){\left|{}_E\sim \mu \right|}_E$, then $f^{\text{'}}\left(x\right)\in \left\{\pm a^r:r\in \mathbb{Q}\right\}$ at $\mu$-a.e. point $x\in f^{-1}E$. In particular, if $g$ is a piecewise-analytic map preserving $\mu$ then there is an open $g$-invariant set $U$ containing supp $\mu$ such that $g\left|{}_U\right.$ is piecewise-linear with slopes which are rational powers of $a$. In a similar vein, for $\mu$ as above, if $b$ is another integer and $a,b$ are not powers of a common integer, and if $\nu$ is a $T_b$-invariant...

We consider groups of orientation-preserving real analytic diffeomorphisms of the circle which have a finite image under the rotation number function. We show that if such a group is nondiscrete with respect to the $C^1$-topology then it has a finite orbit. As a corollary, we show that if such a group has no finite orbit then each of its subgroups contains either a cyclic subgroup of finite index or a nonabelian free subgroup.

We investigate the symbolic dynamics for the double standard maps of the circle onto itself, given by $f_{a,b}\left(x\right)=2x+a+(b/\pi )sin\left(2\pi x\right)\left(mod1\right)$, where b = 1 and a is a real parameter, 0 ≤ a < 1.

On démontre le lemme de Mañé-Conze-Guivarc’h (en classe Lipschitz) pour les systèmes amphidynamiques vérifiant une certaine condition d’hyperbolicité  : la « rectifiabilité ». Diverses applications sont données.

Etant donné $\alpha$ irrationnel de type constant, nous donnons des conditions explicites et génériques sur les pentes d’un homéomorphisme $f$ affine par morceaux du cercle de nombre de rotation $\alpha$, qui garantissent que la mesure de probabilité $f$-invariante est singulière par rapport à la mesure de Haar. Cet article contient une preuve élémentaire d’un résultat de E. Ghys et V. Sergiescu : ”le nombre de rotation d’un homéomorphisme dyadique est rationnel”. Nous y étudions aussi le ratio set des homéomorphismes...

In this paper, recent results on the existence and uniqueness of (continuous and homeomorphic) solutions φ of the equation φ ∘ f = g ∘ φ (f and g are given self-maps of an interval or the circle) are surveyed. Some applications of these results as well as the outcomes concerning systems of such equations are also presented.

We give a necessary and sufficient condition such that, for almost all s ∈ ℝ, ||nθ - s|| < ψ(n) for infinitely many n ∈ ℕ, where θ is fixed and ψ(n) is a positive, non-increasing sequence. This can be seen as a dual result to classical theorems of Khintchine and Szüsz which dealt with the situation where s is fixed and θ is random. Moreover, our result contains several earlier ones as special cases: two old theorems of Kurzweil, a theorem of Tseng and a recent...

We show that for a finitely generated group of C² circle diffeomorphisms, the entropy of the action equals the entropy of the restriction of the action to the non-wandering set.