- #1
Domnu
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Problem
Consider the operator [tex]\hat{C}[/tex] which satisfies the property that [tex]\hat{C} \phi (x) = \phi ^ * (x)[/tex]. Is [tex]\hat{C}[/tex] Hermitian? What are the eigenfunctions and eigenvalues of [tex]\hat{C}[/tex]?
Solution
We have
[tex]\hat{C} \phi = \phi ^ *[/tex]
[tex]\iff \phi^* \hat{C}^\dagger = \phi [/tex]
Substituting back into the first equation,
[tex]\hat{C} (\phi^* \hat{C}^\dagger) = \phi ^ * = \hat{C} \phi[/tex]
[tex]\iff (\hat{C} \phi)(\hat{C} - I) = 0[/tex]
Now, we know that [tex]\hat{C} \phi \neq 0[/tex], since (we assume that) [tex]\phi[/tex] isn't zero... if [tex]\hat{C} = 0,[/tex] then the original property that [tex]\hat{C}[/tex] satisfied couldn't possibly be true. Thus, we have that [tex]\hat{C} = I[/tex], which is clearly Hermitian.
Since [tex]\hat{C}[/tex] is just the identity operator, we know that all functions are the eigenfunctions of [tex]\hat{C}[/tex] and the only eigenvalue of [tex]\hat{C}[/tex] is 1.
Could someone verify that the above is true? It seems too simple =/
Consider the operator [tex]\hat{C}[/tex] which satisfies the property that [tex]\hat{C} \phi (x) = \phi ^ * (x)[/tex]. Is [tex]\hat{C}[/tex] Hermitian? What are the eigenfunctions and eigenvalues of [tex]\hat{C}[/tex]?
Solution
We have
[tex]\hat{C} \phi = \phi ^ *[/tex]
[tex]\iff \phi^* \hat{C}^\dagger = \phi [/tex]
Substituting back into the first equation,
[tex]\hat{C} (\phi^* \hat{C}^\dagger) = \phi ^ * = \hat{C} \phi[/tex]
[tex]\iff (\hat{C} \phi)(\hat{C} - I) = 0[/tex]
Now, we know that [tex]\hat{C} \phi \neq 0[/tex], since (we assume that) [tex]\phi[/tex] isn't zero... if [tex]\hat{C} = 0,[/tex] then the original property that [tex]\hat{C}[/tex] satisfied couldn't possibly be true. Thus, we have that [tex]\hat{C} = I[/tex], which is clearly Hermitian.
Since [tex]\hat{C}[/tex] is just the identity operator, we know that all functions are the eigenfunctions of [tex]\hat{C}[/tex] and the only eigenvalue of [tex]\hat{C}[/tex] is 1.
Could someone verify that the above is true? It seems too simple =/