Convergence question on analytic continuation of Zeta fcn

In summary, the Riemann zeta function converges for all complex s except for s=1. To demonstrate this convergence, one needs to calculate
  • #1
benorin
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Given [itex]\zeta (s) = \sum_{k=1}^{\infty} k^{-s}[/itex] which converges in the half-plane [itex]\Re (s) >1[/itex], the usual analytic continuation to the half-plane [itex]\Re (s) >0[/itex] is found by adding the alternating series [itex]\sum_{k=1}^{\infty} (-1)^kk^{-s}[/itex] to [itex]\zeta (s)[/itex] and simplifing to get

[tex]\zeta (s) = \left(1-2^{1-s}\right) ^{-1}\sum_{k=1}^{\infty} \frac{(-1)^{k-1}}{k^s}[/tex]

now re-index this series to begin with k=0 and apply Euler's series transformation (as given by Knopp: in terms of the backward difference operator; (4) and (5) in the link) to arrive at this series

[tex]\zeta (s) = \left(1-2^{1-s}\right) ^{-1}\sum_{k=0}^{\infty}\frac{1}{2^{k+1}} \sum_{m=0}^{k} \left( \begin{array}{c}k\\m\end{array}\right) \frac{(-1)^{m}}{(m+1)^s}[/tex]

which according to the mathworld Riemann zeta function page formula (20) converges for all s in the complex plane except s=1 (i.e. [itex]\forall s\in\mathbb{C}\setminus \left\{ 1\right\} [/itex] ). My question is, how does one demonstrate the convergence of this series on said domain?

EDIT: I have noticed that

[tex]\zeta (-s) = \left(1-2^{1+s}\right) ^{-1}\sum_{k=0}^{\infty}\frac{1}{2^{k+1}} \sum_{m=0}^{k} \left( \begin{array}{c}k\\m\end{array}\right) (-1)^{m}(m+1)^s[/tex]

does :uhh: not at all appear to converge according to that portion of my "gut" that is known to conjecture for me when initially looking at series for convergence. :biggrin:

Thanks, --Ben
 
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  • #2
See "Analytic Continuation of Riemann's Zeta Function and Values at Negative Integers Via Euler's Transformation of Series", Jonathan Sondow, Proceedings of the American Mathematical Society, Vol. 120, No. 2. (Feb., 1994), pp. 421-424.

If you have access to http://www.jstor.org/cgi-bin/jstor/printpage/00029939/di981511/98p04597/0?frame=noframe&dpi=3&userID=8e9680ea@utoronto.ca/01cc993397005075a23&backcontext=table-of-contents&backurl=/cgi-bin/jstor/listjournal/00029939/di981511%3fframe%3dframe%26dpi%3d3%26userID%3d8e9680ea@utoronto.ca/01cc993397005075a23%26config%3djstor&action=download&config=jstor
 
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  • #3
Thank you for taking the time to dig that one up, shmoe. Much appreciated.
 
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  • #4
I got said article, and it is a nice reference. Thank you shmoe.
 

1. What is analytic continuation of the Zeta function?

The Zeta function is a mathematical function that has important applications in number theory and physics. It is defined as the infinite sum of the reciprocals of all positive integers raised to a given power. Analytic continuation refers to extending the domain of this function beyond its original definition to include complex numbers.

2. Why is the convergence of the Zeta function important?

The convergence of the Zeta function is important because it allows us to evaluate the function at any point in the complex plane, not just at positive real numbers. This is useful in various mathematical and physical applications, such as calculating the distribution of prime numbers and understanding the behavior of quantum systems.

3. What is the Riemann Hypothesis and how does it relate to the convergence of the Zeta function?

The Riemann Hypothesis is a famous unsolved problem in mathematics that states that all non-trivial zeros of the Zeta function lie on the critical line with real part equal to 1/2. In other words, it predicts the location of the points where the Zeta function is equal to zero. Proving the Riemann Hypothesis would provide a deeper understanding of the convergence and behavior of the Zeta function.

4. Are there any known issues with the convergence of the Zeta function?

Yes, there are known issues with the convergence of the Zeta function. One example is the pole at s=1, which makes the function undefined at that point. This is known as the trivial zero and is related to the infinite sum of the reciprocals of all positive integers being divergent. However, this issue can be addressed through analytic continuation.

5. How is the convergence of the Zeta function related to the prime number theorem?

The prime number theorem is a fundamental theorem in number theory that gives an estimate of the number of prime numbers below a given number. It is closely related to the convergence of the Zeta function because the behavior of the Zeta function at certain points is directly linked to the distribution of prime numbers. Specifically, the prime number theorem can be derived from the asymptotic behavior of the Zeta function near the critical line.

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