How Can I Evaluate This Intriguing Integral in Analytic Number Theory?

  • Context: Graduate 
  • Thread starter Thread starter riemannian
  • Start date Start date
  • Tags Tags
    Integral
Join the discussion
Ask a follow-up here, or get your own question answered by working scientists, mathematicians and engineers — people, not an autocomplete.
Real named experts · corrections over time · the nuance an AI answer skips
1 reply · 2K views
riemannian
Messages
5
Reaction score
0
greetings . the following integral appears in some references on analytic number theory . i am really intrigued by it . and would love to understand it .
[tex]\int_{1}^{\infty}\frac{\left \{x \right \}}{x}\left(\frac{1}{x^{s}-1}\right)dx[/tex]

[itex]\Re(s)>1[/itex] , [itex]\left \{x \right \}[/itex] is the fractional , sawtooth function .

i have tried the Fourier expansion of the sawtooth function :

[tex]\int_{1}^{\infty}\frac{\left \{x \right \}}{x}\left(\frac{1}{x^{s}-1}\right)dx = \int_{1}^{\infty}\frac{1}{x(x^{s}-1)}\left(\frac{1}{2}-\frac{1}{\pi}\sum_{n=1}^{\infty}\frac{\sin(2\pi i nx)}{n} \right )dx =\int_{1}^{\infty}\frac{1}{x(x^{s}-1)}\left(\frac{1}{2}+\frac{1}{2\pi i}\ln \left(\frac{1-q^{2}}{1-q^{-2}} \right)\right )dx[/tex]

where [itex]q[/itex] is the nome :
[tex]q=e^{i \pi x}[/tex]

but that brought me no where near a solution ! any suggestions on how to do the integral ??
 
Physics news on Phys.org
after some manipulation , the integral reduces to :

[tex]\frac{1}{2\pi i }\int_{1}^{\infty}\frac{\left(\pi i +\ln(-e^{2\pi i x}) \right )}{x(x^{s}-1)}dx[/tex]