# Homework Help: Infinite Derivative of the Zeta Function

1. Jan 23, 2010

### seanhbailey

1. The problem statement, all variables and given/known data

When extended to the complex plain, does the zeta function approach zero as the number of derivatives of it approaches infinity?

2. Relevant equations

3. The attempt at a solution

2. Jan 23, 2010

### seanhbailey

Could someone please help? I really need an answer.

3. Jan 23, 2010

### Petek

I don't understand the question. When extended to the entire complex plane, the zeta function is analytic everywhere, except at 1. Being analytic implies that it's infinitely differentiable everywhere (again, except at 1). What do you mean by "does the zeta function approach zero as the number of derivatives of it approaches infinity?"

Petek

4. Jan 23, 2010

### seanhbailey

In other words, does the infinith derivative of the zeta function equal 0?

5. Jan 23, 2010

### Petek

I think you're saying that, suppose s $\neq$ 1. Then, does the sequence $(\zeta^{(n)}(s))$ converge to zero? If that's what you mean, I'll have think about it. Let me know if you mean something else.

Petek

6. Jan 23, 2010

### seanhbailey

Yes, that is what I mean.

7. Jan 24, 2010

### Petek

Sorry, can't figure it out. The only result I could get was the trivial observation that

$$\frac{\zeta^{(n)}(s)}{n!}$$

converges to zero for all s $\neq$ 1. That just follows from the fact that zeta is analytic at those points, and hence has a Taylor series whose coefficients are as above. If this is a problem from a book, you might want to check if the previous problem provides a clue. Sometimes authors will do that.

Petek

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