Two examples show that $L^2$ convergence and almost everywhere convergence are independent notions [closed]












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To show the main difference between pointwise ergodic theorem and mean ergodic theorem we have to show that $L^2$ convergence and almost everywhere convergence are independent notions.



Therefore, I am looking for two examples of sequences of functions, the first sequence is $L^2$ convergent but not almost everywhere convergent and the second one is almost everywhere convergent but not $L^2$convergent.










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closed as off-topic by Xander Henderson, Holo, amWhy, Did, Davide Giraudo Jan 8 at 15:45


This question appears to be off-topic. The users who voted to close gave this specific reason:


  • "This question is missing context or other details: Please provide additional context, which ideally explains why the question is relevant to you and our community. Some forms of context include: background and motivation, relevant definitions, source, possible strategies, your current progress, why the question is interesting or important, etc." – amWhy, Did, Davide Giraudo

If this question can be reworded to fit the rules in the help center, please edit the question.









  • 3




    $begingroup$
    You have asked two questions here. The first is "Does convergence in $L^2$ imply almost everywhere convergence?" The second is "Does almost everywhere convergence imply $L^2$ convergence?" Both questions have been answered before.
    $endgroup$
    – Xander Henderson
    Jan 8 at 14:49










  • $begingroup$
    And zero personal input.
    $endgroup$
    – Did
    Jan 8 at 15:06
















-4












$begingroup$


To show the main difference between pointwise ergodic theorem and mean ergodic theorem we have to show that $L^2$ convergence and almost everywhere convergence are independent notions.



Therefore, I am looking for two examples of sequences of functions, the first sequence is $L^2$ convergent but not almost everywhere convergent and the second one is almost everywhere convergent but not $L^2$convergent.










share|cite|improve this question









$endgroup$



closed as off-topic by Xander Henderson, Holo, amWhy, Did, Davide Giraudo Jan 8 at 15:45


This question appears to be off-topic. The users who voted to close gave this specific reason:


  • "This question is missing context or other details: Please provide additional context, which ideally explains why the question is relevant to you and our community. Some forms of context include: background and motivation, relevant definitions, source, possible strategies, your current progress, why the question is interesting or important, etc." – amWhy, Did, Davide Giraudo

If this question can be reworded to fit the rules in the help center, please edit the question.









  • 3




    $begingroup$
    You have asked two questions here. The first is "Does convergence in $L^2$ imply almost everywhere convergence?" The second is "Does almost everywhere convergence imply $L^2$ convergence?" Both questions have been answered before.
    $endgroup$
    – Xander Henderson
    Jan 8 at 14:49










  • $begingroup$
    And zero personal input.
    $endgroup$
    – Did
    Jan 8 at 15:06














-4












-4








-4





$begingroup$


To show the main difference between pointwise ergodic theorem and mean ergodic theorem we have to show that $L^2$ convergence and almost everywhere convergence are independent notions.



Therefore, I am looking for two examples of sequences of functions, the first sequence is $L^2$ convergent but not almost everywhere convergent and the second one is almost everywhere convergent but not $L^2$convergent.










share|cite|improve this question









$endgroup$




To show the main difference between pointwise ergodic theorem and mean ergodic theorem we have to show that $L^2$ convergence and almost everywhere convergence are independent notions.



Therefore, I am looking for two examples of sequences of functions, the first sequence is $L^2$ convergent but not almost everywhere convergent and the second one is almost everywhere convergent but not $L^2$convergent.







functional-analysis measure-theory convergence ergodic-theory






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Jan 8 at 14:41









Neil hawkingNeil hawking

48819




48819




closed as off-topic by Xander Henderson, Holo, amWhy, Did, Davide Giraudo Jan 8 at 15:45


This question appears to be off-topic. The users who voted to close gave this specific reason:


  • "This question is missing context or other details: Please provide additional context, which ideally explains why the question is relevant to you and our community. Some forms of context include: background and motivation, relevant definitions, source, possible strategies, your current progress, why the question is interesting or important, etc." – amWhy, Did, Davide Giraudo

If this question can be reworded to fit the rules in the help center, please edit the question.




closed as off-topic by Xander Henderson, Holo, amWhy, Did, Davide Giraudo Jan 8 at 15:45


This question appears to be off-topic. The users who voted to close gave this specific reason:


  • "This question is missing context or other details: Please provide additional context, which ideally explains why the question is relevant to you and our community. Some forms of context include: background and motivation, relevant definitions, source, possible strategies, your current progress, why the question is interesting or important, etc." – amWhy, Did, Davide Giraudo

If this question can be reworded to fit the rules in the help center, please edit the question.








  • 3




    $begingroup$
    You have asked two questions here. The first is "Does convergence in $L^2$ imply almost everywhere convergence?" The second is "Does almost everywhere convergence imply $L^2$ convergence?" Both questions have been answered before.
    $endgroup$
    – Xander Henderson
    Jan 8 at 14:49










  • $begingroup$
    And zero personal input.
    $endgroup$
    – Did
    Jan 8 at 15:06














  • 3




    $begingroup$
    You have asked two questions here. The first is "Does convergence in $L^2$ imply almost everywhere convergence?" The second is "Does almost everywhere convergence imply $L^2$ convergence?" Both questions have been answered before.
    $endgroup$
    – Xander Henderson
    Jan 8 at 14:49










  • $begingroup$
    And zero personal input.
    $endgroup$
    – Did
    Jan 8 at 15:06








3




3




$begingroup$
You have asked two questions here. The first is "Does convergence in $L^2$ imply almost everywhere convergence?" The second is "Does almost everywhere convergence imply $L^2$ convergence?" Both questions have been answered before.
$endgroup$
– Xander Henderson
Jan 8 at 14:49




$begingroup$
You have asked two questions here. The first is "Does convergence in $L^2$ imply almost everywhere convergence?" The second is "Does almost everywhere convergence imply $L^2$ convergence?" Both questions have been answered before.
$endgroup$
– Xander Henderson
Jan 8 at 14:49












$begingroup$
And zero personal input.
$endgroup$
– Did
Jan 8 at 15:06




$begingroup$
And zero personal input.
$endgroup$
– Did
Jan 8 at 15:06










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