Analytical Integration of a Difficult Function

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Discussion Overview

The discussion revolves around the analytical integration of a specific function involving an integral from 0 to infinity. Participants explore the behavior of the integrand, particularly its boundedness and the implications of coordinate transformations on the integral's convergence.

Discussion Character

  • Technical explanation, Debate/contested, Mathematical reasoning

Main Points Raised

  • One participant asks if the integral is bounded and what coordinate transformation might make it so.
  • Another participant questions the context of the problem, suggesting that integrals of this form arise in the study of chemical reaction rates.
  • A participant notes that the integrand appears to behave well at infinity but raises concerns about its behavior near zero, suggesting a simplification for analysis.
  • Another participant mentions that a tool like WolframAlpha indicates the integral is fine between 0 and β, but suggests that the tail from β to infinity is purely imaginary and infinite.
  • One participant confirms that the expression under the root becomes negative, supporting the claim of the tail being purely imaginary.

Areas of Agreement / Disagreement

Participants express differing views on the behavior of the integral, particularly regarding its boundedness and the nature of its tail. There is no consensus on whether the integral is ultimately integrable or not.

Contextual Notes

Participants discuss the integrand's behavior at both infinity and near zero, indicating potential complexities in determining convergence. The implications of the parameters A, B, and β on the integral's behavior are also noted but not fully resolved.

junt
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Is it possible to integrate the following function analytically?

##\int_{0}^{\infty} \frac{\exp{-(\frac{A}{\tau}+B\tau+\frac{A}{\beta-\tau})}}{\sqrt{\tau(\beta-\tau)}}d\tau,##

where ##A##, ##B## and ##\beta## are real numbers. What sort of coordinate transformation makes the integral bounded? Is it even bounded? Are these poles integrable?

Any help is much appreciated!
 
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Can you provide a context of where you got this problem?
 
jedishrfu said:
Can you provide a context of where you got this problem?
Integrals like this appear when one is looking at chemical reaction rates. The exponent is basically the classical action. A and B contains space coordinates, which will be integrated after integral over ##\tau## has been performed.
 
Hi junt:

I think I understand that you are asking about whether the integral is finite. I think it is easy to see that the integrand behaves OK at infinity. It is a bit trickier to consider behavior at zero. Can you simplify the integrand behavior near zero and see if the integral of the simplification is OK? That is , consider the integral from zero to ε<<1 of a simplified integrand between zero and ε.

Regards,
Buzz
 
I've played a bit with WolframAlpha and it suggests that between 0 and ##\beta## it should be fine but the tail from ##\beta## to ##\infty## is purely imaginary and also infinite.
 
SlowThinker said:
is purely imaginary
Sure, since the expression under the root becomes negative
 

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