Why is it impossible to invert the analytic continuation of a Dirichlet series?












0












$begingroup$


By Mathematica (and the truncated Euler MacLaurin formula) I know that:



$$zeta(s)=lim_{kto infty } , left(sum _{n=1}^k frac{1}{n^s}+frac{1}{(s-1) k^{s-1}}right) tag{1}$$
when the real part of $s$ is greater than $0$.



Question:




I would like to understand better why it is impossible to find a
Dirichlet series for the reciprocal of the Right Hand Side (RHS) of $(1)$.




In other words I am looking for to invert the reciprocal of the Riemann zeta function:



$$frac{1}{zeta(s)}=frac{1}{lim_{kto infty } , left(sum _{n=1}^k frac{1}{n^s}+frac{1}{(s-1) k^{s-1}}right)} tag{2}$$
when the real part of $s$ is greater than $0$.



For $Re(s)>1$ there is the well known relation:



$$frac{1}{zeta(s)}=sum _{n=1}^{infty} frac{mu(n)}{n^s} tag{3}$$



and the Riemann hypothesis is that $(3)$ converges for $Re(s)>frac{1}{2}$.



In a sense I already know the answer to the question. It is because $frac{1}{(s-1) k^{s-1}}$ is like a constant and $sum _{n=1}^k frac{1}{n^s}$ is the Dirichlet series. But can you explain it better to me?










share|cite|improve this question











$endgroup$












  • $begingroup$
    If there was such a Dirichlet series for the reciprocal of the RHS of $(1)$ then a formula for the Riemann zeta zeros would follow after some effort. One could perhaps say that there is no formula for the zeta zeros because the RHS of $(3)$ is an epsilon away from converging on the critical line.
    $endgroup$
    – Mats Granvik
    Jan 20 at 15:23












  • $begingroup$
    You should look at the Dirichlet L-function $beta(s) = lim_{N to infty}sum_{n=0}^N (-1)^n (2n+1)^{-s}$. It converges for $Re(s) > 0$ and iff it has no zeros for $Re(s) > sigma$ then $frac{1}{beta(s)}= sum_{n=0}^infty (-1)^n (2n+1)^{-s} mu(n)$ for $Re(s) >sigma$. For $Re(s)$ large enough $frac{1}{sum_{n=0}^N (-1)^n (2n+1)^{-s}} = sum_{k=0}^infty (1-sum_{n=0}^N (-1)^n (2n+1)^{-s})^k$, once reordered it is a Dirichlet series. It shouldn't converge beyond $Re(s) > 1$. For $zeta$ those things won't be Dirichlet series anymore due to the additional term $frac{N^{1-s}}{s-1}$.
    $endgroup$
    – reuns
    Jan 21 at 12:23








  • 1




    $begingroup$
    Also the explicit formula for $sum_{n le x} mu(n)$ tell us how to regularize/continue $sum_{n=1}^infty mu(n)n^{-s}$ to any vertical strip with no zeros.
    $endgroup$
    – reuns
    Jan 21 at 12:30
















0












$begingroup$


By Mathematica (and the truncated Euler MacLaurin formula) I know that:



$$zeta(s)=lim_{kto infty } , left(sum _{n=1}^k frac{1}{n^s}+frac{1}{(s-1) k^{s-1}}right) tag{1}$$
when the real part of $s$ is greater than $0$.



Question:




I would like to understand better why it is impossible to find a
Dirichlet series for the reciprocal of the Right Hand Side (RHS) of $(1)$.




In other words I am looking for to invert the reciprocal of the Riemann zeta function:



$$frac{1}{zeta(s)}=frac{1}{lim_{kto infty } , left(sum _{n=1}^k frac{1}{n^s}+frac{1}{(s-1) k^{s-1}}right)} tag{2}$$
when the real part of $s$ is greater than $0$.



For $Re(s)>1$ there is the well known relation:



$$frac{1}{zeta(s)}=sum _{n=1}^{infty} frac{mu(n)}{n^s} tag{3}$$



and the Riemann hypothesis is that $(3)$ converges for $Re(s)>frac{1}{2}$.



In a sense I already know the answer to the question. It is because $frac{1}{(s-1) k^{s-1}}$ is like a constant and $sum _{n=1}^k frac{1}{n^s}$ is the Dirichlet series. But can you explain it better to me?










share|cite|improve this question











$endgroup$












  • $begingroup$
    If there was such a Dirichlet series for the reciprocal of the RHS of $(1)$ then a formula for the Riemann zeta zeros would follow after some effort. One could perhaps say that there is no formula for the zeta zeros because the RHS of $(3)$ is an epsilon away from converging on the critical line.
    $endgroup$
    – Mats Granvik
    Jan 20 at 15:23












  • $begingroup$
    You should look at the Dirichlet L-function $beta(s) = lim_{N to infty}sum_{n=0}^N (-1)^n (2n+1)^{-s}$. It converges for $Re(s) > 0$ and iff it has no zeros for $Re(s) > sigma$ then $frac{1}{beta(s)}= sum_{n=0}^infty (-1)^n (2n+1)^{-s} mu(n)$ for $Re(s) >sigma$. For $Re(s)$ large enough $frac{1}{sum_{n=0}^N (-1)^n (2n+1)^{-s}} = sum_{k=0}^infty (1-sum_{n=0}^N (-1)^n (2n+1)^{-s})^k$, once reordered it is a Dirichlet series. It shouldn't converge beyond $Re(s) > 1$. For $zeta$ those things won't be Dirichlet series anymore due to the additional term $frac{N^{1-s}}{s-1}$.
    $endgroup$
    – reuns
    Jan 21 at 12:23








  • 1




    $begingroup$
    Also the explicit formula for $sum_{n le x} mu(n)$ tell us how to regularize/continue $sum_{n=1}^infty mu(n)n^{-s}$ to any vertical strip with no zeros.
    $endgroup$
    – reuns
    Jan 21 at 12:30














0












0








0





$begingroup$


By Mathematica (and the truncated Euler MacLaurin formula) I know that:



$$zeta(s)=lim_{kto infty } , left(sum _{n=1}^k frac{1}{n^s}+frac{1}{(s-1) k^{s-1}}right) tag{1}$$
when the real part of $s$ is greater than $0$.



Question:




I would like to understand better why it is impossible to find a
Dirichlet series for the reciprocal of the Right Hand Side (RHS) of $(1)$.




In other words I am looking for to invert the reciprocal of the Riemann zeta function:



$$frac{1}{zeta(s)}=frac{1}{lim_{kto infty } , left(sum _{n=1}^k frac{1}{n^s}+frac{1}{(s-1) k^{s-1}}right)} tag{2}$$
when the real part of $s$ is greater than $0$.



For $Re(s)>1$ there is the well known relation:



$$frac{1}{zeta(s)}=sum _{n=1}^{infty} frac{mu(n)}{n^s} tag{3}$$



and the Riemann hypothesis is that $(3)$ converges for $Re(s)>frac{1}{2}$.



In a sense I already know the answer to the question. It is because $frac{1}{(s-1) k^{s-1}}$ is like a constant and $sum _{n=1}^k frac{1}{n^s}$ is the Dirichlet series. But can you explain it better to me?










share|cite|improve this question











$endgroup$




By Mathematica (and the truncated Euler MacLaurin formula) I know that:



$$zeta(s)=lim_{kto infty } , left(sum _{n=1}^k frac{1}{n^s}+frac{1}{(s-1) k^{s-1}}right) tag{1}$$
when the real part of $s$ is greater than $0$.



Question:




I would like to understand better why it is impossible to find a
Dirichlet series for the reciprocal of the Right Hand Side (RHS) of $(1)$.




In other words I am looking for to invert the reciprocal of the Riemann zeta function:



$$frac{1}{zeta(s)}=frac{1}{lim_{kto infty } , left(sum _{n=1}^k frac{1}{n^s}+frac{1}{(s-1) k^{s-1}}right)} tag{2}$$
when the real part of $s$ is greater than $0$.



For $Re(s)>1$ there is the well known relation:



$$frac{1}{zeta(s)}=sum _{n=1}^{infty} frac{mu(n)}{n^s} tag{3}$$



and the Riemann hypothesis is that $(3)$ converges for $Re(s)>frac{1}{2}$.



In a sense I already know the answer to the question. It is because $frac{1}{(s-1) k^{s-1}}$ is like a constant and $sum _{n=1}^k frac{1}{n^s}$ is the Dirichlet series. But can you explain it better to me?







elementary-number-theory analytic-number-theory riemann-zeta dirichlet-series






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Jan 20 at 15:23









J. W. Tanner

2,1371117




2,1371117










asked Jan 20 at 15:14









Mats GranvikMats Granvik

3,29132250




3,29132250












  • $begingroup$
    If there was such a Dirichlet series for the reciprocal of the RHS of $(1)$ then a formula for the Riemann zeta zeros would follow after some effort. One could perhaps say that there is no formula for the zeta zeros because the RHS of $(3)$ is an epsilon away from converging on the critical line.
    $endgroup$
    – Mats Granvik
    Jan 20 at 15:23












  • $begingroup$
    You should look at the Dirichlet L-function $beta(s) = lim_{N to infty}sum_{n=0}^N (-1)^n (2n+1)^{-s}$. It converges for $Re(s) > 0$ and iff it has no zeros for $Re(s) > sigma$ then $frac{1}{beta(s)}= sum_{n=0}^infty (-1)^n (2n+1)^{-s} mu(n)$ for $Re(s) >sigma$. For $Re(s)$ large enough $frac{1}{sum_{n=0}^N (-1)^n (2n+1)^{-s}} = sum_{k=0}^infty (1-sum_{n=0}^N (-1)^n (2n+1)^{-s})^k$, once reordered it is a Dirichlet series. It shouldn't converge beyond $Re(s) > 1$. For $zeta$ those things won't be Dirichlet series anymore due to the additional term $frac{N^{1-s}}{s-1}$.
    $endgroup$
    – reuns
    Jan 21 at 12:23








  • 1




    $begingroup$
    Also the explicit formula for $sum_{n le x} mu(n)$ tell us how to regularize/continue $sum_{n=1}^infty mu(n)n^{-s}$ to any vertical strip with no zeros.
    $endgroup$
    – reuns
    Jan 21 at 12:30


















  • $begingroup$
    If there was such a Dirichlet series for the reciprocal of the RHS of $(1)$ then a formula for the Riemann zeta zeros would follow after some effort. One could perhaps say that there is no formula for the zeta zeros because the RHS of $(3)$ is an epsilon away from converging on the critical line.
    $endgroup$
    – Mats Granvik
    Jan 20 at 15:23












  • $begingroup$
    You should look at the Dirichlet L-function $beta(s) = lim_{N to infty}sum_{n=0}^N (-1)^n (2n+1)^{-s}$. It converges for $Re(s) > 0$ and iff it has no zeros for $Re(s) > sigma$ then $frac{1}{beta(s)}= sum_{n=0}^infty (-1)^n (2n+1)^{-s} mu(n)$ for $Re(s) >sigma$. For $Re(s)$ large enough $frac{1}{sum_{n=0}^N (-1)^n (2n+1)^{-s}} = sum_{k=0}^infty (1-sum_{n=0}^N (-1)^n (2n+1)^{-s})^k$, once reordered it is a Dirichlet series. It shouldn't converge beyond $Re(s) > 1$. For $zeta$ those things won't be Dirichlet series anymore due to the additional term $frac{N^{1-s}}{s-1}$.
    $endgroup$
    – reuns
    Jan 21 at 12:23








  • 1




    $begingroup$
    Also the explicit formula for $sum_{n le x} mu(n)$ tell us how to regularize/continue $sum_{n=1}^infty mu(n)n^{-s}$ to any vertical strip with no zeros.
    $endgroup$
    – reuns
    Jan 21 at 12:30
















$begingroup$
If there was such a Dirichlet series for the reciprocal of the RHS of $(1)$ then a formula for the Riemann zeta zeros would follow after some effort. One could perhaps say that there is no formula for the zeta zeros because the RHS of $(3)$ is an epsilon away from converging on the critical line.
$endgroup$
– Mats Granvik
Jan 20 at 15:23






$begingroup$
If there was such a Dirichlet series for the reciprocal of the RHS of $(1)$ then a formula for the Riemann zeta zeros would follow after some effort. One could perhaps say that there is no formula for the zeta zeros because the RHS of $(3)$ is an epsilon away from converging on the critical line.
$endgroup$
– Mats Granvik
Jan 20 at 15:23














$begingroup$
You should look at the Dirichlet L-function $beta(s) = lim_{N to infty}sum_{n=0}^N (-1)^n (2n+1)^{-s}$. It converges for $Re(s) > 0$ and iff it has no zeros for $Re(s) > sigma$ then $frac{1}{beta(s)}= sum_{n=0}^infty (-1)^n (2n+1)^{-s} mu(n)$ for $Re(s) >sigma$. For $Re(s)$ large enough $frac{1}{sum_{n=0}^N (-1)^n (2n+1)^{-s}} = sum_{k=0}^infty (1-sum_{n=0}^N (-1)^n (2n+1)^{-s})^k$, once reordered it is a Dirichlet series. It shouldn't converge beyond $Re(s) > 1$. For $zeta$ those things won't be Dirichlet series anymore due to the additional term $frac{N^{1-s}}{s-1}$.
$endgroup$
– reuns
Jan 21 at 12:23






$begingroup$
You should look at the Dirichlet L-function $beta(s) = lim_{N to infty}sum_{n=0}^N (-1)^n (2n+1)^{-s}$. It converges for $Re(s) > 0$ and iff it has no zeros for $Re(s) > sigma$ then $frac{1}{beta(s)}= sum_{n=0}^infty (-1)^n (2n+1)^{-s} mu(n)$ for $Re(s) >sigma$. For $Re(s)$ large enough $frac{1}{sum_{n=0}^N (-1)^n (2n+1)^{-s}} = sum_{k=0}^infty (1-sum_{n=0}^N (-1)^n (2n+1)^{-s})^k$, once reordered it is a Dirichlet series. It shouldn't converge beyond $Re(s) > 1$. For $zeta$ those things won't be Dirichlet series anymore due to the additional term $frac{N^{1-s}}{s-1}$.
$endgroup$
– reuns
Jan 21 at 12:23






1




1




$begingroup$
Also the explicit formula for $sum_{n le x} mu(n)$ tell us how to regularize/continue $sum_{n=1}^infty mu(n)n^{-s}$ to any vertical strip with no zeros.
$endgroup$
– reuns
Jan 21 at 12:30




$begingroup$
Also the explicit formula for $sum_{n le x} mu(n)$ tell us how to regularize/continue $sum_{n=1}^infty mu(n)n^{-s}$ to any vertical strip with no zeros.
$endgroup$
– reuns
Jan 21 at 12:30










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