From: guyeux Date: Fri, 1 Jun 2012 17:26:58 +0000 (+0200) Subject: fldhvcd,vdclkdjflkjgldsfjldsknlck,lkcjlkjdlkfjlsqkdjflqsdlkjflkd X-Git-Url: https://bilbo.iut-bm.univ-fcomte.fr/and/gitweb/review_prng.git/commitdiff_plain/d8286f1f28ed46780c8a9943ff22a09a1905aa55?ds=sidebyside fldhvcd,vdclkdjflkjgldsfjldsknlck,lkcjlkjdlkfjlsqkdjflqsdlkjflkd dfdsf --- diff --git a/review_prng.tex b/review_prng.tex index b395874..f595d05 100644 --- a/review_prng.tex +++ b/review_prng.tex @@ -232,7 +232,7 @@ With all this material, the study of chaotic iterations as a discrete dynamical system has then be realized. This study is summarized in the next section. -\subsection{Topological Properties of Chaotic Iterations} +\subsection{A Topology for Chaotic Iterations} The topological space on which chaotic iterations are defined has firstly been investigated, leading to the following result~\cite{gb11:bc,GuyeuxThese10}: @@ -253,7 +253,7 @@ of period $k$ for $f$, we have $\forall k \in \mathds{N}, Per_{2k+1}(G_{f_0}) = \varnothing, card\left(Per_{2k+2}(G_{f_0})\right)>0$. \end{proposition} -So $\Rightarrow G_{f_0}$ does not present the existence of points of any period referred as chaos in the article of Li and Yorke~\cite{Li75}. +So $ G_{f_0}$ does not present the existence of points of any period referred as chaos in the article of Li and Yorke~\cite{Li75}. However~\cite{GuyeuxThese10}: \begin{itemize} \item This kind of disorder can be stated on $\mathcal{X}^G = \mathcal{P}\left(\llbracket 1,\mathsf{N}\rrbracket\right)^\mathds{N}\times \mathds{B}^\mathsf{N}$. @@ -262,6 +262,14 @@ However~\cite{GuyeuxThese10}: Additionally, this existence of points of any period has been rejected by the community to the benefit of more recent notions of chaos, like those developed these last decades by Devaney~\cite{Devaney}, Knudsen~\cite{Knudsen94}, etc. +These approaches are recalled in the next section. + +\section{The Mathematical Theory of Chaos} + +We will present in this section various understanding of a chaotic behavior for a discrete +dynamical system. + +\subsection{Approaches Similar to Devaney} In these approaches, three ingredients are required for unpredictability. Firstly, the system must be intrinsically complicated, undecomposable: it cannot be simplified into two @@ -298,34 +306,22 @@ not equivalent one another, like: \end{itemize} -Concerning the ingredient of sensibility, it can be formulated as follows. - -%\frame{ -%\frametitle{Stabilité et expansivité} -% \begin{block}{Définitions de la sensibilité} -% \begin{itemize} -% \item $(\mathcal{X},f)$ est \emph{instable} si tous ses points le sont: $\forall x \in \mathcal{X},$ $\exists \varepsilon >0,$ $\forall \delta > 0,$ $\exists y \in \mathcal{X},$ $\exists n \in \mathbb{N},$ $d(x,y)<\delta$ et $d(f^{(n)}(x),f^{(n)}(y)) \geqslant \varepsilon$ -% \item $(\mathcal{X},f)$ est \emph{expansif} si -%$\exists \varepsilon >0,$ $\forall x \neq y,$ $\exists n \in \mathbb{N},$ $d(f^{(n)}(x),f^{(n)}(y)) \geqslant \varepsilon$ -% \end{itemize} -% \end{block} -%} +Concerning the ingredient of sensibility, it can be reformulated as follows. +\begin{itemize} + \item $(\mathcal{X},f)$ is \emph{unstable} is all its points are unstable: $\forall x \in \mathcal{X},$ $\exists \varepsilon >0,$ $\forall \delta > 0,$ $\exists y \in \mathcal{X},$ $\exists n \in \mathbb{N},$ $d(x,y)<\delta$ and $d(f^{(n)}(x),f^{(n)}(y)) \geqslant \varepsilon$. + \item $(\mathcal{X},f)$ is \emph{expansive} is $\exists \varepsilon >0,$ $\forall x \neq y,$ $\exists n \in \mathbb{N},$ $d(f^{(n)}(x),f^{(n)}(y)) \geqslant \varepsilon$ +\end{itemize} -%%\frame{ -%% \frametitle{Des systèmes imprévisibles} -%% \begin{block}{Définitions des systèmes dynamiques désordonnés} -%% \begin{itemize} -%% \item \emph{Devaney:} $(\mathcal{X},f)$ est sensible aux conditions initiales, régulier et transitif -%% \item \emph{Wiggins:} $(\mathcal{X},f)$ est transitif et sensible aux conditions initiales -%% \item \emph{Knudsen:} $(\mathcal{X},f)$ a une orbite dense et s'il est sensible aux conditions initiales -%% \item \emph{expansif:} $(\mathcal{X},f)$ est transitif, régulier et expansif -%% \end{itemize} -%% \end{block} -%%} +These variety of definitions lead to various notions of chaos. For instance, +a dynamical system is chaotic according to Wiggins if it is transitive and +sensible to the initial conditions. It is said chaotic according to Knudsen +if it has a dense orbit while being sensible. Finally, we speak about +expansive chaos when the properties of transitivity, regularity, and expansivity +are satisfied. -%\subsection*{Autres approches} +\subsection{Other approaches} %\frame{