Theorem 3.29 in Baby Rudin












4












$begingroup$


Theorem 3.29 in Walter Rudin's Principles of Mathematical Analysis, 3rd ed., states that




If $p>1$, then the series $$sum_{n=2}^infty frac{1}{n (log n)^p} $$ converges; if $p leq 1$, the series diverges.




Now in the proof, Rudin only seems to discuss the case when $p> 0$, for it is only in this particular case that we can use the Cauchy Condensation Test.



How to deal with the case of $p<0$?



Of course, the case $p=0$ yields the divergent harmonic series.










share|cite|improve this question











$endgroup$

















    4












    $begingroup$


    Theorem 3.29 in Walter Rudin's Principles of Mathematical Analysis, 3rd ed., states that




    If $p>1$, then the series $$sum_{n=2}^infty frac{1}{n (log n)^p} $$ converges; if $p leq 1$, the series diverges.




    Now in the proof, Rudin only seems to discuss the case when $p> 0$, for it is only in this particular case that we can use the Cauchy Condensation Test.



    How to deal with the case of $p<0$?



    Of course, the case $p=0$ yields the divergent harmonic series.










    share|cite|improve this question











    $endgroup$















      4












      4








      4





      $begingroup$


      Theorem 3.29 in Walter Rudin's Principles of Mathematical Analysis, 3rd ed., states that




      If $p>1$, then the series $$sum_{n=2}^infty frac{1}{n (log n)^p} $$ converges; if $p leq 1$, the series diverges.




      Now in the proof, Rudin only seems to discuss the case when $p> 0$, for it is only in this particular case that we can use the Cauchy Condensation Test.



      How to deal with the case of $p<0$?



      Of course, the case $p=0$ yields the divergent harmonic series.










      share|cite|improve this question











      $endgroup$




      Theorem 3.29 in Walter Rudin's Principles of Mathematical Analysis, 3rd ed., states that




      If $p>1$, then the series $$sum_{n=2}^infty frac{1}{n (log n)^p} $$ converges; if $p leq 1$, the series diverges.




      Now in the proof, Rudin only seems to discuss the case when $p> 0$, for it is only in this particular case that we can use the Cauchy Condensation Test.



      How to deal with the case of $p<0$?



      Of course, the case $p=0$ yields the divergent harmonic series.







      calculus real-analysis sequences-and-series analysis convergence






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      share|cite|improve this question













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      edited Dec 26 '18 at 18:22







      Saaqib Mahmood

















      asked Oct 22 '14 at 4:36









      Saaqib MahmoodSaaqib Mahmood

      7,95942581




      7,95942581






















          2 Answers
          2






          active

          oldest

          votes


















          7












          $begingroup$

          The case of $p<0$ is trivial, since
          $$sum_{k=2}^infty frac{ln^{-p} k}{k}gesum_{k=4}^infty frac{1}{k}.$$






          share|cite|improve this answer









          $endgroup$





















            0












            $begingroup$

            You can use the integral test:



            $$ sum_{n geq 2 }frac{1}{n ( log n )^p} cong intlimits_2^{infty} frac{dz}{z (log z )^p} = intlimits_{2}^{infty} frac{ d(log z)}{ ( log z )^p }= ...$$






            share|cite|improve this answer









            $endgroup$









            • 2




              $begingroup$
              The integral test is not to be used; I'd like to do a a theorem in Rudin and so use the same armory that he's given me uptil this point.
              $endgroup$
              – Saaqib Mahmood
              Oct 25 '14 at 3:38












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            2 Answers
            2






            active

            oldest

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            2 Answers
            2






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes









            7












            $begingroup$

            The case of $p<0$ is trivial, since
            $$sum_{k=2}^infty frac{ln^{-p} k}{k}gesum_{k=4}^infty frac{1}{k}.$$






            share|cite|improve this answer









            $endgroup$


















              7












              $begingroup$

              The case of $p<0$ is trivial, since
              $$sum_{k=2}^infty frac{ln^{-p} k}{k}gesum_{k=4}^infty frac{1}{k}.$$






              share|cite|improve this answer









              $endgroup$
















                7












                7








                7





                $begingroup$

                The case of $p<0$ is trivial, since
                $$sum_{k=2}^infty frac{ln^{-p} k}{k}gesum_{k=4}^infty frac{1}{k}.$$






                share|cite|improve this answer









                $endgroup$



                The case of $p<0$ is trivial, since
                $$sum_{k=2}^infty frac{ln^{-p} k}{k}gesum_{k=4}^infty frac{1}{k}.$$







                share|cite|improve this answer












                share|cite|improve this answer



                share|cite|improve this answer










                answered Oct 22 '14 at 4:38









                Hanul JeonHanul Jeon

                17.7k42881




                17.7k42881























                    0












                    $begingroup$

                    You can use the integral test:



                    $$ sum_{n geq 2 }frac{1}{n ( log n )^p} cong intlimits_2^{infty} frac{dz}{z (log z )^p} = intlimits_{2}^{infty} frac{ d(log z)}{ ( log z )^p }= ...$$






                    share|cite|improve this answer









                    $endgroup$









                    • 2




                      $begingroup$
                      The integral test is not to be used; I'd like to do a a theorem in Rudin and so use the same armory that he's given me uptil this point.
                      $endgroup$
                      – Saaqib Mahmood
                      Oct 25 '14 at 3:38
















                    0












                    $begingroup$

                    You can use the integral test:



                    $$ sum_{n geq 2 }frac{1}{n ( log n )^p} cong intlimits_2^{infty} frac{dz}{z (log z )^p} = intlimits_{2}^{infty} frac{ d(log z)}{ ( log z )^p }= ...$$






                    share|cite|improve this answer









                    $endgroup$









                    • 2




                      $begingroup$
                      The integral test is not to be used; I'd like to do a a theorem in Rudin and so use the same armory that he's given me uptil this point.
                      $endgroup$
                      – Saaqib Mahmood
                      Oct 25 '14 at 3:38














                    0












                    0








                    0





                    $begingroup$

                    You can use the integral test:



                    $$ sum_{n geq 2 }frac{1}{n ( log n )^p} cong intlimits_2^{infty} frac{dz}{z (log z )^p} = intlimits_{2}^{infty} frac{ d(log z)}{ ( log z )^p }= ...$$






                    share|cite|improve this answer









                    $endgroup$



                    You can use the integral test:



                    $$ sum_{n geq 2 }frac{1}{n ( log n )^p} cong intlimits_2^{infty} frac{dz}{z (log z )^p} = intlimits_{2}^{infty} frac{ d(log z)}{ ( log z )^p }= ...$$







                    share|cite|improve this answer












                    share|cite|improve this answer



                    share|cite|improve this answer










                    answered Oct 22 '14 at 4:42







                    user139708















                    • 2




                      $begingroup$
                      The integral test is not to be used; I'd like to do a a theorem in Rudin and so use the same armory that he's given me uptil this point.
                      $endgroup$
                      – Saaqib Mahmood
                      Oct 25 '14 at 3:38














                    • 2




                      $begingroup$
                      The integral test is not to be used; I'd like to do a a theorem in Rudin and so use the same armory that he's given me uptil this point.
                      $endgroup$
                      – Saaqib Mahmood
                      Oct 25 '14 at 3:38








                    2




                    2




                    $begingroup$
                    The integral test is not to be used; I'd like to do a a theorem in Rudin and so use the same armory that he's given me uptil this point.
                    $endgroup$
                    – Saaqib Mahmood
                    Oct 25 '14 at 3:38




                    $begingroup$
                    The integral test is not to be used; I'd like to do a a theorem in Rudin and so use the same armory that he's given me uptil this point.
                    $endgroup$
                    – Saaqib Mahmood
                    Oct 25 '14 at 3:38


















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