The hermitian conjugate/adjoint -Quantum Physics

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Homework Help Overview

The discussion revolves around the concept of the hermitian conjugate (or adjoint) of operators in quantum physics, specifically focusing on the properties and manipulation of these operators. The original poster presents a problem involving the expression of the hermitian conjugate of a sum of operators.

Discussion Character

  • Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants explore the application of the hermitian conjugate properties, questioning how to separate operators and apply the integral condition provided in the problem. There is a discussion about the manipulation of operators and their algebraic behavior.

Discussion Status

Some participants have offered suggestions on how to approach the problem, including the use of the integral condition to separate terms. Others express confusion regarding the manipulation of operators and the implications of the problem's wording. The discussion appears to be productive, with participants building on each other's ideas.

Contextual Notes

There is an indication that the original poster feels uncertain about their understanding of operator manipulation, which may affect their approach to the problem. The complexity of the question and its marking weight is also noted as a point of concern.

Calcifur
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Homework Statement



The hermitian conjugate of an operator, [itex]\hat{F}[/itex], written [itex]\hat{F}[/itex][itex]^{\tau}[/itex] satisfies the condition:

∫∅*(r)[itex]\hat{F}[/itex][itex]^{\tau}[/itex]ψ(r)dr=(∫ψ*(r)[itex]\hat{F}[/itex]∅(r)dr)*

for any choice of wavefunctions ψ and ∅. Show that:

([itex]\hat{F}[/itex]+i[itex]\hat{G}[/itex])[itex]^{\tau}[/itex]=[itex]\hat{F}[/itex][itex]^{\tau}[/itex] -i[itex]\hat{G}[/itex][itex]^{\tau}[/itex]

(10 marks)
2. The attempt at a solution

I feel like I'm missing something here, either that or the question's stupidly easily and isn't worth ten marks.
As ((A + B)* = A* + B*) and as with all complex conjugates (x+iy)*=(x-iy), it can be applied to the above as it's still just a complex conjugate. I know I'm supposed to use the condition above somehow so without obviously telling me the answer, could someone point me in the right direction for how I'm supposed to SHOW it please.
 
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did you try using (F+iG) as an operator and then using the
∫∅*(r)Fˆτψ(r)dr=(∫ψ*(r)Fˆ∅(r)dr)* and seperating them while they are in (... )* and then apply
∫∅*(r)Fˆτψ(r)dr=(∫ψ*(r)Fˆ∅(r)dr)* in reverse way ? not sure but that may help.
 
Hmmm. Yes, I can sort of see what you mean. I've tried it but I'm still confused with how the τ's are allowed to be separated. I think it's due to the question being worded in a confusing way. If I knew how operators could be manipulated algebraically then I'd probably get somewhere...I'm assuming they don't function like normal variables?
 
∫∅*(r)(Fˆ+iGˆ)τψ(r)dr=(∫ψ*(r)(Fˆ+iGˆ)∅(r)dr)*
=(∫ψ*(r)(Fˆ)∅(r)dr+i∫ψ*(r)Gˆ(r)∅(r)dr)*
=((∫∅*(r)Fˆτψ(r)dr)*+i(∫∅*(r)Gˆτψ(r)dr)*)*
 
crimsonidol said:
∫∅*(r)(Fˆ+iGˆ)τψ(r)dr=(∫ψ*(r)(Fˆ+iGˆ)∅(r)dr)*
=(∫ψ*(r)(Fˆ)∅(r)dr+i∫ψ*(r)Gˆ(r)∅(r)dr)*
=((∫∅*(r)Fˆτψ(r)dr)*+i(∫∅*(r)Gˆτψ(r)dr)*)*

Brilliant... I understand it now thanks crimsonidol!
 

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