$frac{1}{||x||^n}$ is integrable on complement of $B(0,a) subset mathbb{R}^n$











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I am trying to prove that for a measurable function $f$, the Hardy-Littlewood maximal function is not in $L^1$ unless $f$ is $0$ a.e.



I was able to udnerstand the proof of the inequality here with $1$ replaced by an arbitrary constant $a>0$ : A question about the Hardy-Littlewood maximal function.



However I want to conclude by saying that Mf is not integrable since $1/|x|^n$ is not integrable on $B(0,a)^c$. Is this true? Am I thinking in the right direction?



EDIT: I found this in Frank Jones' measure theory book: https://imgur.com/a/tct1vI2. So it seems to be true, I just have no clue why it should be true.










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    up vote
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    down vote

    favorite












    I am trying to prove that for a measurable function $f$, the Hardy-Littlewood maximal function is not in $L^1$ unless $f$ is $0$ a.e.



    I was able to udnerstand the proof of the inequality here with $1$ replaced by an arbitrary constant $a>0$ : A question about the Hardy-Littlewood maximal function.



    However I want to conclude by saying that Mf is not integrable since $1/|x|^n$ is not integrable on $B(0,a)^c$. Is this true? Am I thinking in the right direction?



    EDIT: I found this in Frank Jones' measure theory book: https://imgur.com/a/tct1vI2. So it seems to be true, I just have no clue why it should be true.










    share|cite|improve this question


























      up vote
      0
      down vote

      favorite









      up vote
      0
      down vote

      favorite











      I am trying to prove that for a measurable function $f$, the Hardy-Littlewood maximal function is not in $L^1$ unless $f$ is $0$ a.e.



      I was able to udnerstand the proof of the inequality here with $1$ replaced by an arbitrary constant $a>0$ : A question about the Hardy-Littlewood maximal function.



      However I want to conclude by saying that Mf is not integrable since $1/|x|^n$ is not integrable on $B(0,a)^c$. Is this true? Am I thinking in the right direction?



      EDIT: I found this in Frank Jones' measure theory book: https://imgur.com/a/tct1vI2. So it seems to be true, I just have no clue why it should be true.










      share|cite|improve this question















      I am trying to prove that for a measurable function $f$, the Hardy-Littlewood maximal function is not in $L^1$ unless $f$ is $0$ a.e.



      I was able to udnerstand the proof of the inequality here with $1$ replaced by an arbitrary constant $a>0$ : A question about the Hardy-Littlewood maximal function.



      However I want to conclude by saying that Mf is not integrable since $1/|x|^n$ is not integrable on $B(0,a)^c$. Is this true? Am I thinking in the right direction?



      EDIT: I found this in Frank Jones' measure theory book: https://imgur.com/a/tct1vI2. So it seems to be true, I just have no clue why it should be true.







      real-analysis measure-theory






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      edited Nov 17 at 8:57

























      asked Nov 17 at 8:50









      HerrWarum

      15911




      15911






















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          It is true and it follows immediately if you use polar coordinates in $mathbb R^{n}$. Look for 'polar coordinates' in the index of Rudin's RCA.






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            It is true and it follows immediately if you use polar coordinates in $mathbb R^{n}$. Look for 'polar coordinates' in the index of Rudin's RCA.






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              up vote
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              It is true and it follows immediately if you use polar coordinates in $mathbb R^{n}$. Look for 'polar coordinates' in the index of Rudin's RCA.






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                up vote
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                up vote
                0
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                It is true and it follows immediately if you use polar coordinates in $mathbb R^{n}$. Look for 'polar coordinates' in the index of Rudin's RCA.






                share|cite|improve this answer












                It is true and it follows immediately if you use polar coordinates in $mathbb R^{n}$. Look for 'polar coordinates' in the index of Rudin's RCA.







                share|cite|improve this answer












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                answered Nov 17 at 12:01









                Kavi Rama Murthy

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