Definition of ergodic map












3












$begingroup$


I ask the similar question before. About definition of Ergodic theorem.
Now just sincerely ask another fundamental problem about the definition of ergodic map.



The following definition is what I read in my textbook:




Let $(X,mathcal{A},mu)$ be a probability space. Let $T: Xrightarrow X$ is $mu$-invariant ($mu$-preserving). Then $T$ is ergodic if for every $Ein mathcal{A}$ with $T^{-1}(E) = E$ if and only if $mu(E)=0$ or $1$.




In this definition, it requires $T^{-1}(E) = E$. However, in the following paper, it seems to use $T(E) = E$ as the definition.



https://www.tandfonline.com/doi/abs/10.1080/10236190601045788 (p.1154, Def 2.16, please also see "$A$ is invariant, i.e. $T(A)=A$ on the top of that page.")



My questions are:




  1. What is the difference between them? or is the definition in the paper not correct?

  2. For the definition by using $T^{-1}(E) = E$, does it imply $E$ is not an attractor? since the only initial condition such that $T(x_0) in E$ is $x_0 in E$ instead of $x_0in Xsetminus E$.


So if we want to discuss $E$ being an attractor, we have to use $T(E) = E$ since this could imply the possibility that $T(x)in E$ for $xin Xsetminus E$. Do I make sense?



Thanks in advance.










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$endgroup$








  • 1




    $begingroup$
    If $T$ is invertible then these definition are equivalent.
    $endgroup$
    – Yanko
    Jan 27 at 11:51
















3












$begingroup$


I ask the similar question before. About definition of Ergodic theorem.
Now just sincerely ask another fundamental problem about the definition of ergodic map.



The following definition is what I read in my textbook:




Let $(X,mathcal{A},mu)$ be a probability space. Let $T: Xrightarrow X$ is $mu$-invariant ($mu$-preserving). Then $T$ is ergodic if for every $Ein mathcal{A}$ with $T^{-1}(E) = E$ if and only if $mu(E)=0$ or $1$.




In this definition, it requires $T^{-1}(E) = E$. However, in the following paper, it seems to use $T(E) = E$ as the definition.



https://www.tandfonline.com/doi/abs/10.1080/10236190601045788 (p.1154, Def 2.16, please also see "$A$ is invariant, i.e. $T(A)=A$ on the top of that page.")



My questions are:




  1. What is the difference between them? or is the definition in the paper not correct?

  2. For the definition by using $T^{-1}(E) = E$, does it imply $E$ is not an attractor? since the only initial condition such that $T(x_0) in E$ is $x_0 in E$ instead of $x_0in Xsetminus E$.


So if we want to discuss $E$ being an attractor, we have to use $T(E) = E$ since this could imply the possibility that $T(x)in E$ for $xin Xsetminus E$. Do I make sense?



Thanks in advance.










share|cite|improve this question









$endgroup$








  • 1




    $begingroup$
    If $T$ is invertible then these definition are equivalent.
    $endgroup$
    – Yanko
    Jan 27 at 11:51














3












3








3





$begingroup$


I ask the similar question before. About definition of Ergodic theorem.
Now just sincerely ask another fundamental problem about the definition of ergodic map.



The following definition is what I read in my textbook:




Let $(X,mathcal{A},mu)$ be a probability space. Let $T: Xrightarrow X$ is $mu$-invariant ($mu$-preserving). Then $T$ is ergodic if for every $Ein mathcal{A}$ with $T^{-1}(E) = E$ if and only if $mu(E)=0$ or $1$.




In this definition, it requires $T^{-1}(E) = E$. However, in the following paper, it seems to use $T(E) = E$ as the definition.



https://www.tandfonline.com/doi/abs/10.1080/10236190601045788 (p.1154, Def 2.16, please also see "$A$ is invariant, i.e. $T(A)=A$ on the top of that page.")



My questions are:




  1. What is the difference between them? or is the definition in the paper not correct?

  2. For the definition by using $T^{-1}(E) = E$, does it imply $E$ is not an attractor? since the only initial condition such that $T(x_0) in E$ is $x_0 in E$ instead of $x_0in Xsetminus E$.


So if we want to discuss $E$ being an attractor, we have to use $T(E) = E$ since this could imply the possibility that $T(x)in E$ for $xin Xsetminus E$. Do I make sense?



Thanks in advance.










share|cite|improve this question









$endgroup$




I ask the similar question before. About definition of Ergodic theorem.
Now just sincerely ask another fundamental problem about the definition of ergodic map.



The following definition is what I read in my textbook:




Let $(X,mathcal{A},mu)$ be a probability space. Let $T: Xrightarrow X$ is $mu$-invariant ($mu$-preserving). Then $T$ is ergodic if for every $Ein mathcal{A}$ with $T^{-1}(E) = E$ if and only if $mu(E)=0$ or $1$.




In this definition, it requires $T^{-1}(E) = E$. However, in the following paper, it seems to use $T(E) = E$ as the definition.



https://www.tandfonline.com/doi/abs/10.1080/10236190601045788 (p.1154, Def 2.16, please also see "$A$ is invariant, i.e. $T(A)=A$ on the top of that page.")



My questions are:




  1. What is the difference between them? or is the definition in the paper not correct?

  2. For the definition by using $T^{-1}(E) = E$, does it imply $E$ is not an attractor? since the only initial condition such that $T(x_0) in E$ is $x_0 in E$ instead of $x_0in Xsetminus E$.


So if we want to discuss $E$ being an attractor, we have to use $T(E) = E$ since this could imply the possibility that $T(x)in E$ for $xin Xsetminus E$. Do I make sense?



Thanks in advance.







measure-theory operator-theory ergodic-theory






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asked Jan 21 at 9:38









sleeve chensleeve chen

3,14042053




3,14042053








  • 1




    $begingroup$
    If $T$ is invertible then these definition are equivalent.
    $endgroup$
    – Yanko
    Jan 27 at 11:51














  • 1




    $begingroup$
    If $T$ is invertible then these definition are equivalent.
    $endgroup$
    – Yanko
    Jan 27 at 11:51








1




1




$begingroup$
If $T$ is invertible then these definition are equivalent.
$endgroup$
– Yanko
Jan 27 at 11:51




$begingroup$
If $T$ is invertible then these definition are equivalent.
$endgroup$
– Yanko
Jan 27 at 11:51










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