From: zeraoulia on
Hello to all,
My question is: let the alternating serie ∑ (-1)
**n-1*an*exp(i*β*ln(n))=0, where (an) is real and i is the complex
number, ln(n) is the logaritm of n. The sum is taken over all natural
numbers n>=1. I wonder if the above equation (the serie=0) implies
that all the coefficents an=0 for all n. I appreciate if one can help
me to find an answer with some references.
From: Gerry Myerson on
In article
<6011a022-4c5c-4e44-a011-bce855788c73(a)b35g2000yqi.googlegroups.com>,
zeraoulia <zelhadj12(a)gmail.com> wrote:

> Hello to all,
> My question is: let the alternating serie � (-1)
> **n-1*an*exp(i*ɿ*ln(n))=0, where (an) is real and i is the complex
> number, ln(n) is the logaritm of n. The sum is taken over all natural
> numbers n>=1. I wonder if the above equation (the serie=0) implies
> that all the coefficents an=0 for all n. I appreciate if one can help
> me to find an answer with some references.

1. Don't use special characters in a text-based newsgroup.
What looked like a beta to you looks like gobbledygook once
my machine has had its way.

2. It's not an alternating series. That term makes sense only
for real series.

3. The (-1)^(n - 1) seems to be superfluous, as it can be absorbed
into the a_n, so we have sum a_n exp( i b log n) = 0.

4. What is beta? Is the equation supposed to hold for all beta?
or just for one fixed value of beta? is beta real?

--
Gerry Myerson (gerry(a)maths.mq.edi.ai) (i -> u for email)
From: Robert Israel on
On Wed, 09 Jun 2010 08:52:14 +1000, Gerry Myerson wrote:

> In article
> <6011a022-4c5c-4e44-a011-bce855788c73(a)b35g2000yqi.googlegroups.com>,
> zeraoulia <zelhadj12(a)gmail.com> wrote:
>
>> Hello to all,
>> My question is: let the alternating serie � (-1)
>> **n-1*an*exp(i*ɿ*ln(n))=0, where (an) is real and i is the complex
>> number, ln(n) is the logaritm of n. The sum is taken over all natural
>> numbers n>=1. I wonder if the above equation (the serie=0) implies
>> that all the coefficents an=0 for all n. I appreciate if one can help
>> me to find an answer with some references.
>
> 1. Don't use special characters in a text-based newsgroup.
> What looked like a beta to you looks like gobbledygook once
> my machine has had its way.
>
> 2. It's not an alternating series. That term makes sense only
> for real series.
>
> 3. The (-1)^(n - 1) seems to be superfluous, as it can be absorbed
> into the a_n, so we have sum a_n exp( i b log n) = 0.
>
> 4. What is beta? Is the equation supposed to hold for all beta?
> or just for one fixed value of beta? is beta real?

Writing the series as sum a_n n^(i beta), what we have is a Dirichlet
series. If it ever converges, there is some r such that the series
converges uniformly on U = {beta in C: Im(beta) > r}, and the sum is
analytic on that set. If that analytic function is 0 for beta in some
set that has a limit point in U, it must be 0 for all beta in U.
And then by a standard result on uniqueness for Dirichlet series, the
answer is yes. See e.g. Theorem 3D in
<http://rutherglen.ics.mq.edu.au/wchen/lndpnfolder/dpn03-ds.pdf>

--
Robert Israel israel(a)math.MyUniversitysInitials.ca
Department of Mathematics http://www.math.ubc.ca/~israel
University of British Columbia Vancouver, BC, Canada
From: zeraoulia on
On Jun 9, 12:52 am, Gerry Myerson <ge...(a)maths.mq.edi.ai.i2u4email>
wrote:
> In article
> <6011a022-4c5c-4e44-a011-bce855788...(a)b35g2000yqi.googlegroups.com>,
>
>  zeraoulia <zelhad...(a)gmail.com> wrote:
> > Hello to all,
> > My question is: let the alternating serie … (-1)
> > **n-1*an*exp(i*É¿*ln(n))=0, where (an) is real and i is the complex
> > number, ln(n) is the logaritm of n. The sum is taken over all natural
> > numbers n>=1.  I wonder if the above equation (the serie=0) implies
> > that all the coefficents an=0 for all n. I appreciate if one can help
> > me to find an answer with some references.
>
> 1. Don't use special characters in a text-based newsgroup.
> What looked like a beta to you looks like gobbledygook once
> my machine has had its way.
>
> 2. It's not an alternating series. That term makes sense only
> for real series.
>
> 3. The (-1)^(n - 1) seems to be superfluous, as it can be absorbed
> into the a_n, so we have sum a_n exp( i b log n) = 0.
>
> 4. What is beta? Is the equation supposed to hold for all beta?
> or just for one fixed value of beta? is beta real?
>
> --
> Gerry Myerson (ge...(a)maths.mq.edi.ai) (i -> u for email)

The coefficient (-1)^(n - 1) is not superfluous in the equation. The
number beta is real and the equation supposed to hold for one fixed
value of beta.
Thank you
From: zeraoulia on
On Jun 9, 4:20 am, Robert Israel
<isr...(a)math.MyUniversitysInitials.ca> wrote:
> On Wed, 09 Jun 2010 08:52:14 +1000, Gerry Myerson wrote:
> > In article
> > <6011a022-4c5c-4e44-a011-bce855788...(a)b35g2000yqi.googlegroups.com>,
> >  zeraoulia <zelhad...(a)gmail.com> wrote:
>
> >> Hello to all,
> >> My question is: let the alternating serie … (-1)
> >> **n-1*an*exp(i*É¿*ln(n))=0, where (an) is real and i is the complex
> >> number, ln(n) is the logaritm of n. The sum is taken over all natural
> >> numbers n>=1.  I wonder if the above equation (the serie=0) implies
> >> that all the coefficents an=0 for all n. I appreciate if one can help
> >> me to find an answer with some references.
>
> > 1. Don't use special characters in a text-based newsgroup.
> > What looked like a beta to you looks like gobbledygook once
> > my machine has had its way.
>
> > 2. It's not an alternating series. That term makes sense only
> > for real series.
>
> > 3. The (-1)^(n - 1) seems to be superfluous, as it can be absorbed
> > into the a_n, so we have sum a_n exp( i b log n) = 0.
>
> > 4. What is beta? Is the equation supposed to hold for all beta?
> > or just for one fixed value of beta? is beta real?
>
> Writing the series as sum a_n n^(i beta), what we have is a Dirichlet
> series.  If it ever converges, there is some r such that the series
> converges uniformly on U = {beta in C: Im(beta) > r}, and the sum is
> analytic on that set. If that analytic function is 0 for beta in some  
> set that has a limit point in U, it must be 0 for all beta in U.
> And then by a standard result on uniqueness for Dirichlet series, the
> answer is yes.  See e.g. Theorem 3D in
> <http://rutherglen.ics.mq.edu.au/wchen/lndpnfolder/dpn03-ds.pdf>
>
> --
> Robert Israel              isr...(a)math.MyUniversitysInitials.ca
> Department of Mathematics        http://www.math.ubc.ca/~israel
> University of British Columbia            Vancouver, BC, Canada- Hide quoted text -
>
> - Show quoted text -

Thank you very much