QM Integral and Online Integral Tables

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Discussion Overview

The discussion revolves around an integral from Quantum Mechanics, specifically the integral \(\int_{-\infty}^{\infty} A e^{-(x-a)^2} dx\). Participants explore the availability of online integral tables and methods for solving the integral, including substitutions and transformations.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • Jeremy inquires about accessible online integral tables for a specific integral from Quantum Mechanics.
  • Some participants question whether \(A\) is a constant or a matrix, with Daniel suggesting it should be clarified if \(A\) is dependent on \(x\).
  • Jeremy clarifies that \(A\) is indeed a constant, which leads to further discussion on the integral's solvability.
  • Daniel proposes that the integral can be reduced to a Poisson integral using a substitution and applying the theorem of Fubini and polar coordinates.
  • Another participant suggests squaring the integral and transforming to polar coordinates, indicating that no antiderivative exists in terms of familiar functions.
  • A specific case is mentioned where if \(a = 0\) and \(A = 1\), the result is \(\sqrt{\pi}\).

Areas of Agreement / Disagreement

Participants generally agree on the nature of \(A\) as a constant and discuss methods for solving the integral, but there is no consensus on the existence of an antiderivative or the best approach to take.

Contextual Notes

The discussion includes assumptions about the nature of \(A\) and the conditions under which the integral can be simplified, but these aspects remain unresolved in terms of broader applicability.

longbusy
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Hello, I am hung up on an integral from Quantum Mechanics. I searched on Yahoo and Google for online integral tables, but failed to discover anything beyond very basic tables. The integral is as follows:

\int_{-\infty}^{\infty} \(A*e^{-(x-a)^2} dx

Are there any decent online integral tables that are accessible to just anyone? I found some online databases but quickly found out that I had to subscribe.

Thank You,
Jeremy
 
Last edited:
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Is A just a constant or a matrix?
 
cronxeh said:
Is A just a constant or a matrix?

The appropriate question would have bee:is A "x" dependent or not?


Daniel.
 
Oops, sorry, A is a constant. It is not dependent upon x. I could have just left that out.
 
In that case,it can be reduced (by a simple substitution) to a Poisson integral which is doable appling the thoerem of Fubini and polar plane coordinates...

Daniel.
 
What he means is, square the integral and transform to polar coordinates, then use u-substitution (inverse chain rule) to solve an easy integral, take the square root of the result.

As a side note, it is impossible to find an antiderivative for your integral. No antiderivative exits (in terms of familiar functions).

As a side-side note, if a = 0 and A = 1, the answer is sqrt(pi)
 

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