A very interesting complex beta integral:

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Discussion Overview

The discussion revolves around a specific complex integral involving parameters \(a\) and \(b\), with participants exploring its proof and connections to known integrals, particularly the beta integral. The scope includes mathematical reasoning and exploratory discussions on integral calculus.

Discussion Character

  • Exploratory
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant presents the integral and asks for proof, expressing interest in its properties.
  • Another participant inquires whether \(a\) and/or \(b\) are integers, suggesting that this could affect the proof.
  • A different participant assumes \(a\) and \(b\) are integers for simplicity, indicating a potential restriction.
  • Some participants suggest using residues, referencing a method similar to the broomwich integral.
  • One participant expresses doubt about finding a solution using the residue method and asks for the source of the integral.
  • A later reply introduces the Third (Cauchy's) beta integral, indicating that the original integral can be derived from it through substitution, and cites a paper by Vadim Kuznetsov as the source of this information.

Areas of Agreement / Disagreement

Participants have not reached a consensus on the proof of the integral or the conditions under which it holds. There are multiple viewpoints regarding the assumptions about \(a\) and \(b\), and the methods to approach the proof remain contested.

Contextual Notes

There are limitations regarding the assumptions about the parameters \(a\) and \(b\), and the discussion does not resolve the mathematical steps necessary for a complete proof. The relationship between the presented integral and the Third beta integral is noted but not fully explored.

alyafey22
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This is one of the most interesting integrals I've ever seen

$$\frac{1}{2\pi i }\int^{c+i\infty}_{c-i\infty}t^{-a} (1-t)^{-b-1}\, dt = \frac{1}{b\,\beta(a,b)}$$

Does anybody have any idea how to prove it ?
 
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ZaidAlyafey said:
This is one of the most interesting integrals I've ever seen

$$\frac{1}{2\pi i }\int^{c+i\infty}_{c-i\infty}t^{-a} (1-t)^{-b-1}\, dt = \frac{1}{b\,\beta(a,b)}$$

Does anybody have any idea how to prove it ?

Hi ZaidAlyafey, :)

Is \(a\) and/or \(b\) integers?
 
Sudharaka said:
Hi ZaidAlyafey, :)

Is \(a\) and/or \(b\) integers?

Hi, when first I saw this equality there didn't seem to be this restriction , but let us
assume for simplicity that a and b are integers.
 
I guess you are thinking about using residues in a way similar to the broomwich integral.
 
ZaidAlyafey said:
I guess you are thinking about using residues in a way similar to the broomwich integral.

Yeah, but I don't think I can find a way to get the required answer using that method. Where did you find this integral?
 
Sudharaka said:
Yeah, but I don't think I can find a way to get the required answer using that method. Where did you find this integral?

Well, after searching I got that which is called the Third(Cauchy's) beta integral :

$$\int^{\infty}_{-\infty}\frac{dt}{(1-it)^a(1+it)^b}= \frac{\pi 2^{2-a-b}\Gamma{(a+b-1)}}{\Gamma(a)\Gamma(b)}$$

Clearly our integral can be derived by doing a substitution , so this is a general formula
I found this in a paper SPECIAL FUNCTIONS AND THEIR SYMMETRIES by Vadim KUZNETSOV.
 

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