Does the Parity Operator Commute with All Hermitian Operators?

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Discussion Overview

The discussion centers on the question of whether the parity operator commutes with all Hermitian operators, exploring the implications and conditions under which this might be true. Participants examine the properties of the parity operator in relation to various Hermitian operators, including specific examples and counterexamples.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant questions how to prove that the parity operator commutes with Hermitian operators, noting that they can only show that the parity operator itself is Hermitian.
  • Another participant describes the action of the parity operator on wave functions, suggesting that this could facilitate proving the necessary commutation relations.
  • A request is made for a demonstration of the commutation relation with a specific Hermitian operator.
  • In response, a participant emphasizes the need to specify which Hermitian operator is being considered for the commutation calculation.
  • It is noted that the parity operator does not commute with certain operators, such as position and momentum, but does commute with others like orbital angular momentum and spin.
  • Some participants express concern that the original question may be flawed if it implies that the parity operator commutes with all Hermitian operators.

Areas of Agreement / Disagreement

Participants generally disagree on the implications of the question regarding the parity operator's commutation with all Hermitian operators, with some asserting that the question is incorrect if it implies universal commutation.

Contextual Notes

There is a lack of consensus on the conditions under which the parity operator commutes with specific Hermitian operators, and the discussion highlights the need for clarity regarding which operators are being referenced.

roshan2004
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In my terminal exam I was asked to prove it that the parity operation commutes with Hermitian operator? I wonder how can we show that? coz we can only show that the parity operator is hermitian? We haven't got the value of hermitian operator at all?
 
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On wave functions the parity operator acts something like

[tex]P\psi(x)=\eta\psi(-x)[/tex]

where \eta is a phase factor independent of x. Now it should be easy to prove all the commutation relations you need.
 
Pls Can you show it to me how?
 
I can try, but first you have to tell me which is the operator you want to calculate the commutator with parity.
 
Hermitian operator
 
roshan2004 said:
Hermitian operator

It's not enough. For example, P does not commute with the coordinates x or the momenta p (these anticommute with parity), but it commutes with orbital agular momentum or spin...
 
So, wasn't the question a wrong one?
 
If it really implied that the parity operator commutes with all Hermitian operators, then yes, it was wrong.
 

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