Proof that the linear momentum operator is hermitian

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Discussion Overview

The discussion revolves around the proof of whether the linear momentum operator \( P_x \) is Hermitian. Participants are examining a proposed solution and discussing the necessary conditions and properties related to the operator's domain and the wave functions involved.

Discussion Character

  • Technical explanation, Debate/contested, Conceptual clarification

Main Points Raised

  • One participant identifies a sign error in the proposed solution and suggests that further explanation is needed regarding the boundary condition \( \left.\psi_b^*\psi_a\right|_{-\infty}^\infty=0 \).
  • Another participant questions the domain of the linear momentum operator, indicating that arbitrary wave functions may not satisfy the required boundary conditions, and suggests restricting to special wave functions.
  • A different approach involving "distributional differentiation" is mentioned as an alternative method for addressing the problem.
  • A participant asks if using a special function that satisfies the boundary condition would validate their solution.
  • Another participant expresses agreement that the solution appears acceptable if the appropriate conditions are met.

Areas of Agreement / Disagreement

Participants express differing views on the validity of the proposed solution based on the domain of the wave functions and the boundary conditions. There is no consensus on the overall correctness of the proof, as it depends on the specific functions used.

Contextual Notes

Limitations include the need to specify the domain of the linear momentum operator and the requirement for wave functions to meet certain boundary conditions for the proof to hold.

Paul Black
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hello
i have to proof that Px (linear momentum operator ) is hermitian or not
i have added my solution in attachments

please look at my solution and tell me if its correct


thank you all
 

Attachments

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There's a sign error in the last expression of the first page, but you "fixed" it in the next expression.

This looks OK to me, but of course you should explain why ##\left.\psi_b^*\psi_a\right|_{-\infty}^\infty=0##.
 
What is the domain of the linear momentum operator that you're looking at? You can't just look at arbirary wave functions, because then ##\psi_b^*\psi_a\vert_{-\infty}^{+\infty}## will not be zero. You need to restrict to special wave function which do have that property.

Another solution is that you use "distributional differentiation".
 
thank you for your answers
if i take a special function which satisfy the property then is my solution ok?
 
Yea, it looks OK to me.
 
ok thank you very much
 

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