Help with proof of eq. 2.64 of Intro. to Quantum Mechanics

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Discussion Overview

The discussion revolves around the proof of equation 2.64 from "Introduction to Quantum Mechanics" by Griffiths, specifically focusing on the integral relationship involving the operators related to the harmonic oscillator problem. Participants seek clarification and a more detailed step-by-step proof of the equation presented in the text.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant requests a more elaborate proof of the integral equation involving the operators related to the harmonic oscillator.
  • Another participant questions whether the roots a+ and a- are real, suggesting that if they are, the proof may be justified.
  • A participant explains the behavior of the operator $$\frac{d}{dx}$$ under hermitian conjugation, noting that it picks up a minus sign when applied to functions that vanish at infinity, and relates this to the operators $$\hat{a}_+$$ and $$\hat{a}_-$$.
  • A later reply corrects an earlier statement regarding the roots a+ and a-, asserting that they are not simply roots of the Hamiltonian due to a constant difference of ##\hbar\omega##.

Areas of Agreement / Disagreement

Participants express differing views on the nature of the roots a+ and a-, with one asserting they are not simply roots of the Hamiltonian, indicating a lack of consensus on this point. The discussion remains unresolved regarding the proof and the implications of the operators involved.

Contextual Notes

There are unresolved assumptions regarding the nature of the roots a+ and a-, as well as the conditions under which the integral equation holds. The discussion also highlights the dependence on the definitions of the operators and the context of the proof.

SherLOCKed
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I am self studying the Book- Introduction to Quantum Mechanics , 2e. Griffith. Page 47.
While the book has given a proof for eq. 2.64 but its not very ellaborate
Integral(infinity,-infinity) [f*(a±g(x)).dx] = Integral(infinity,-infinity) [(a±f)* g(x).dx] . It would be great help if somebody could provide me a more step by step proof of the same.
Where a+ and a- are roots of Hamiltonian of harmonic oscillator problem.
 
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Are a+ and a- real? If so it would be justified.
 
The operator

$${d \over dx}$$ picks up a minus sign under hermitian conjugation when the hilbert space is that of functions that vanish fast enough at infinity. The reason why that's true is because:

$$\int f {d g \over dx} = 0 - \int g {df \over dx} dx$$

This implies that when you take the hermitian conjugate of the $\hat{a}_+$ operator, just replace ${d \over dx}$ by $-{d \over dx}$ which gives the $\hat{a}_-$ operator
 
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SherLOCKed said:
Where a+ and a- are roots of Hamiltonian of harmonic oscillator
Be careful there: they are not! There is a constant ##\hbar\omega## difference !
 

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