Integration seems gaussian but the answer does not match

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SUMMARY

The discussion centers on the integration of the Gaussian function, specifically the expression involving the second derivative of \( e^{-bx^2} \). The user initially calculated the integral and arrived at \( \frac{h^2b}{m} \), while the correct result should be \( \frac{h^2b}{2m} \). A key insight provided is that the user miscalculated the integral, leading to a factor of 2 discrepancy, as the correct evaluation yields \( -b \sqrt{\frac{\pi}{2b}} \) instead of \( -2b \sqrt{\frac{\pi}{2b}} \).

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  • Understanding of Gaussian integrals
  • Familiarity with differentiation of exponential functions
  • Knowledge of second derivatives in calculus
  • Basic principles of quantum mechanics related to wave functions
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  • Review Gaussian integration techniques
  • Study the properties of the exponential function \( e^{-bx^2} \)
  • Learn about the application of second derivatives in integrals
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tfhub
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Homework Statement



-h^2/2m (sqrt(2b/pi)) e^(-bx^2) d^2/dx^2 (e^(-bx^2)) dx from - to + infinity

Homework Equations


I tried differentiating e^(-bx^2) twice and it came up weird , I positioned the values and finally cam up with (-2b sqrt(pi/2b)...is there any other way to do it ?

The Attempt at a Solution


I tried with gaussian integration and my final answer is h^2b/m but it should be h^2b/2m... how am i missing the 1/2 factor?
 
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It is difficult to say where you are going wrong if you do not show us exactly what you did step by step.
 
tfhub said:

Homework Statement



-h^2/2m (sqrt(2b/pi)) e^(-bx^2) d^2/dx^2 (e^(-bx^2)) dx from - to + infinity

Homework Equations


I tried differentiating e^(-bx^2) twice and it came up weird , I positioned the values and finally cam up with (-2b sqrt(pi/2b)...is there any other way to do it ?

The Attempt at a Solution


I tried with gaussian integration and my final answer is h^2b/m but it should be h^2b/2m... how am i missing the 1/2 factor?

If you mean that you came up with -2b sqrt(pi/2b) for the integral--that is, that
\int_{-\infty}^{\infty} e^{-bx^2} \frac{d^2}{dx^2} e^{-b x^2} \, dx =- 2b \sqrt{\frac{\pi}{2b}},
then you are off by a factor or 2: you should have ##-b \sqrt{\pi/2b}##. You need to show your work in detail.
 

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