Small question in a proposition involving Ergodicity

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Ergodicity -- A measure preserving transformation T on the space (X, $mathcalB$, $mu$) is called Ergodic iff $forall$ B $inmathcalB$ satisfying T$^-1$B = B we have $mu$(B) = 0 or 1.



Let T be a measure preserving transformation of a space (X, $mathcalB$, $mu$). Then the following are equivalent:



  1. T is ergodic;


  2. For all f $in$ L$^1$ (X, $mathcalB$, $mu$) satisfying f $circ$ T = f a.e. then f is constant a.e.


The book I am reading says that "we can replace L$^1$ in above proposition by measurable or L$^2". Why is that true? Can anyone help me on this?







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  • Have you seen the proof of $1. iff 2.$? If so, look at the proof, you should see that it doesn't matter whether $f $ belongs to $L^1$ or $L^2$. i.e the same proof applies.
    – Zestylemonzi
    40 mins ago















up vote
0
down vote

favorite












Ergodicity -- A measure preserving transformation T on the space (X, $mathcalB$, $mu$) is called Ergodic iff $forall$ B $inmathcalB$ satisfying T$^-1$B = B we have $mu$(B) = 0 or 1.



Let T be a measure preserving transformation of a space (X, $mathcalB$, $mu$). Then the following are equivalent:



  1. T is ergodic;


  2. For all f $in$ L$^1$ (X, $mathcalB$, $mu$) satisfying f $circ$ T = f a.e. then f is constant a.e.


The book I am reading says that "we can replace L$^1$ in above proposition by measurable or L$^2". Why is that true? Can anyone help me on this?







share|cite|improve this question



















  • Have you seen the proof of $1. iff 2.$? If so, look at the proof, you should see that it doesn't matter whether $f $ belongs to $L^1$ or $L^2$. i.e the same proof applies.
    – Zestylemonzi
    40 mins ago













up vote
0
down vote

favorite









up vote
0
down vote

favorite











Ergodicity -- A measure preserving transformation T on the space (X, $mathcalB$, $mu$) is called Ergodic iff $forall$ B $inmathcalB$ satisfying T$^-1$B = B we have $mu$(B) = 0 or 1.



Let T be a measure preserving transformation of a space (X, $mathcalB$, $mu$). Then the following are equivalent:



  1. T is ergodic;


  2. For all f $in$ L$^1$ (X, $mathcalB$, $mu$) satisfying f $circ$ T = f a.e. then f is constant a.e.


The book I am reading says that "we can replace L$^1$ in above proposition by measurable or L$^2". Why is that true? Can anyone help me on this?







share|cite|improve this question











Ergodicity -- A measure preserving transformation T on the space (X, $mathcalB$, $mu$) is called Ergodic iff $forall$ B $inmathcalB$ satisfying T$^-1$B = B we have $mu$(B) = 0 or 1.



Let T be a measure preserving transformation of a space (X, $mathcalB$, $mu$). Then the following are equivalent:



  1. T is ergodic;


  2. For all f $in$ L$^1$ (X, $mathcalB$, $mu$) satisfying f $circ$ T = f a.e. then f is constant a.e.


The book I am reading says that "we can replace L$^1$ in above proposition by measurable or L$^2". Why is that true? Can anyone help me on this?









share|cite|improve this question










share|cite|improve this question




share|cite|improve this question









asked 55 mins ago









HumbleStudent

628311




628311











  • Have you seen the proof of $1. iff 2.$? If so, look at the proof, you should see that it doesn't matter whether $f $ belongs to $L^1$ or $L^2$. i.e the same proof applies.
    – Zestylemonzi
    40 mins ago

















  • Have you seen the proof of $1. iff 2.$? If so, look at the proof, you should see that it doesn't matter whether $f $ belongs to $L^1$ or $L^2$. i.e the same proof applies.
    – Zestylemonzi
    40 mins ago
















Have you seen the proof of $1. iff 2.$? If so, look at the proof, you should see that it doesn't matter whether $f $ belongs to $L^1$ or $L^2$. i.e the same proof applies.
– Zestylemonzi
40 mins ago





Have you seen the proof of $1. iff 2.$? If so, look at the proof, you should see that it doesn't matter whether $f $ belongs to $L^1$ or $L^2$. i.e the same proof applies.
– Zestylemonzi
40 mins ago
















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