Why isn't $zeta(3) = 2^3pi ^{3-1}sinleft( frac{pi 3}{2}right)Gamma(1-3)zeta(1-3) = 0$?












1












$begingroup$


The zeta function (for $Re(s)>1$) is given by the definition:




  1. $zeta(s) = sum _{n=1}^{infty} left [frac{1}{n^s} right]$


The zeta function also can be given by the following functional equation:




  1. $zeta(s) = 2^spi ^{s-1}sinleft( frac{pi s}{2}right)Gamma(1-s)zeta(1-s)$


Using the above functional equation, we also know than for all negative even integers (i.e. $s=-2, -4, -6...$) the zeta function has trivial zeroes i.e.
$zeta(-2) = 0$, $zeta(-4) = 0$, $zeta(-6) = 0$ and so on.



Substituting $s=3$ in the functional equation we have:



a. $zeta(3) = sum _{n=1}^{infty} left [frac{1}{n^3} right]$



b. $zeta(3) = 2^3pi ^{3-1}sinleft( frac{pi 3}{2}right)Gamma(1-3)zeta(1-3)$



Since, $zeta(1-3)=zeta(-2)=0$, using this in the R.H.S of the functional equation (b.) seems to state that $zeta(3) = 0$. But, using (a.) we know that the $zeta(3)$ is convergent but not equal to zero.



So, these two values are different. What is it that I am missing in the functional definition and where is the discrepancy?



P.S. I am from a C.S. background and a beginner in analysis still trying to learn.










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  • $begingroup$
    "The zeta function is given by the definition: 1. $zeta(s) = sum _{n=1}^{infty} left [frac{1}{n^s} right]$" For the record, this is the definition of $zeta(s)$ only when $Re s>1$.
    $endgroup$
    – Did
    Feb 2 at 9:43










  • $begingroup$
    Yes. I was a bit loose with the definition.
    $endgroup$
    – TheoryQuest1
    Feb 2 at 9:50
















1












$begingroup$


The zeta function (for $Re(s)>1$) is given by the definition:




  1. $zeta(s) = sum _{n=1}^{infty} left [frac{1}{n^s} right]$


The zeta function also can be given by the following functional equation:




  1. $zeta(s) = 2^spi ^{s-1}sinleft( frac{pi s}{2}right)Gamma(1-s)zeta(1-s)$


Using the above functional equation, we also know than for all negative even integers (i.e. $s=-2, -4, -6...$) the zeta function has trivial zeroes i.e.
$zeta(-2) = 0$, $zeta(-4) = 0$, $zeta(-6) = 0$ and so on.



Substituting $s=3$ in the functional equation we have:



a. $zeta(3) = sum _{n=1}^{infty} left [frac{1}{n^3} right]$



b. $zeta(3) = 2^3pi ^{3-1}sinleft( frac{pi 3}{2}right)Gamma(1-3)zeta(1-3)$



Since, $zeta(1-3)=zeta(-2)=0$, using this in the R.H.S of the functional equation (b.) seems to state that $zeta(3) = 0$. But, using (a.) we know that the $zeta(3)$ is convergent but not equal to zero.



So, these two values are different. What is it that I am missing in the functional definition and where is the discrepancy?



P.S. I am from a C.S. background and a beginner in analysis still trying to learn.










share|cite|improve this question











$endgroup$












  • $begingroup$
    "The zeta function is given by the definition: 1. $zeta(s) = sum _{n=1}^{infty} left [frac{1}{n^s} right]$" For the record, this is the definition of $zeta(s)$ only when $Re s>1$.
    $endgroup$
    – Did
    Feb 2 at 9:43










  • $begingroup$
    Yes. I was a bit loose with the definition.
    $endgroup$
    – TheoryQuest1
    Feb 2 at 9:50














1












1








1





$begingroup$


The zeta function (for $Re(s)>1$) is given by the definition:




  1. $zeta(s) = sum _{n=1}^{infty} left [frac{1}{n^s} right]$


The zeta function also can be given by the following functional equation:




  1. $zeta(s) = 2^spi ^{s-1}sinleft( frac{pi s}{2}right)Gamma(1-s)zeta(1-s)$


Using the above functional equation, we also know than for all negative even integers (i.e. $s=-2, -4, -6...$) the zeta function has trivial zeroes i.e.
$zeta(-2) = 0$, $zeta(-4) = 0$, $zeta(-6) = 0$ and so on.



Substituting $s=3$ in the functional equation we have:



a. $zeta(3) = sum _{n=1}^{infty} left [frac{1}{n^3} right]$



b. $zeta(3) = 2^3pi ^{3-1}sinleft( frac{pi 3}{2}right)Gamma(1-3)zeta(1-3)$



Since, $zeta(1-3)=zeta(-2)=0$, using this in the R.H.S of the functional equation (b.) seems to state that $zeta(3) = 0$. But, using (a.) we know that the $zeta(3)$ is convergent but not equal to zero.



So, these two values are different. What is it that I am missing in the functional definition and where is the discrepancy?



P.S. I am from a C.S. background and a beginner in analysis still trying to learn.










share|cite|improve this question











$endgroup$




The zeta function (for $Re(s)>1$) is given by the definition:




  1. $zeta(s) = sum _{n=1}^{infty} left [frac{1}{n^s} right]$


The zeta function also can be given by the following functional equation:




  1. $zeta(s) = 2^spi ^{s-1}sinleft( frac{pi s}{2}right)Gamma(1-s)zeta(1-s)$


Using the above functional equation, we also know than for all negative even integers (i.e. $s=-2, -4, -6...$) the zeta function has trivial zeroes i.e.
$zeta(-2) = 0$, $zeta(-4) = 0$, $zeta(-6) = 0$ and so on.



Substituting $s=3$ in the functional equation we have:



a. $zeta(3) = sum _{n=1}^{infty} left [frac{1}{n^3} right]$



b. $zeta(3) = 2^3pi ^{3-1}sinleft( frac{pi 3}{2}right)Gamma(1-3)zeta(1-3)$



Since, $zeta(1-3)=zeta(-2)=0$, using this in the R.H.S of the functional equation (b.) seems to state that $zeta(3) = 0$. But, using (a.) we know that the $zeta(3)$ is convergent but not equal to zero.



So, these two values are different. What is it that I am missing in the functional definition and where is the discrepancy?



P.S. I am from a C.S. background and a beginner in analysis still trying to learn.







real-analysis complex-analysis riemann-zeta






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edited Feb 2 at 14:28









user21820

40.2k544162




40.2k544162










asked Feb 2 at 9:19









TheoryQuest1TheoryQuest1

1498




1498












  • $begingroup$
    "The zeta function is given by the definition: 1. $zeta(s) = sum _{n=1}^{infty} left [frac{1}{n^s} right]$" For the record, this is the definition of $zeta(s)$ only when $Re s>1$.
    $endgroup$
    – Did
    Feb 2 at 9:43










  • $begingroup$
    Yes. I was a bit loose with the definition.
    $endgroup$
    – TheoryQuest1
    Feb 2 at 9:50


















  • $begingroup$
    "The zeta function is given by the definition: 1. $zeta(s) = sum _{n=1}^{infty} left [frac{1}{n^s} right]$" For the record, this is the definition of $zeta(s)$ only when $Re s>1$.
    $endgroup$
    – Did
    Feb 2 at 9:43










  • $begingroup$
    Yes. I was a bit loose with the definition.
    $endgroup$
    – TheoryQuest1
    Feb 2 at 9:50
















$begingroup$
"The zeta function is given by the definition: 1. $zeta(s) = sum _{n=1}^{infty} left [frac{1}{n^s} right]$" For the record, this is the definition of $zeta(s)$ only when $Re s>1$.
$endgroup$
– Did
Feb 2 at 9:43




$begingroup$
"The zeta function is given by the definition: 1. $zeta(s) = sum _{n=1}^{infty} left [frac{1}{n^s} right]$" For the record, this is the definition of $zeta(s)$ only when $Re s>1$.
$endgroup$
– Did
Feb 2 at 9:43












$begingroup$
Yes. I was a bit loose with the definition.
$endgroup$
– TheoryQuest1
Feb 2 at 9:50




$begingroup$
Yes. I was a bit loose with the definition.
$endgroup$
– TheoryQuest1
Feb 2 at 9:50










1 Answer
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The function $Gamma$ has a pole at every non-positive integer. The pole of $Gamma$ at $-2$ "cancels out" the zero of $zeta$ at $-2$ since they are both simple.






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    1 Answer
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    $begingroup$

    The function $Gamma$ has a pole at every non-positive integer. The pole of $Gamma$ at $-2$ "cancels out" the zero of $zeta$ at $-2$ since they are both simple.






    share|cite|improve this answer











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      10












      $begingroup$

      The function $Gamma$ has a pole at every non-positive integer. The pole of $Gamma$ at $-2$ "cancels out" the zero of $zeta$ at $-2$ since they are both simple.






      share|cite|improve this answer











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        10












        10








        10





        $begingroup$

        The function $Gamma$ has a pole at every non-positive integer. The pole of $Gamma$ at $-2$ "cancels out" the zero of $zeta$ at $-2$ since they are both simple.






        share|cite|improve this answer











        $endgroup$



        The function $Gamma$ has a pole at every non-positive integer. The pole of $Gamma$ at $-2$ "cancels out" the zero of $zeta$ at $-2$ since they are both simple.







        share|cite|improve this answer














        share|cite|improve this answer



        share|cite|improve this answer








        edited Feb 2 at 9:42









        Did

        249k23228466




        249k23228466










        answered Feb 2 at 9:27









        asdasd

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