- #1
peaco99
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Homework Statement
[itex]\hat{A}[/itex] is an anti-unitary operator, and it is known that [itex]\hat{A^2}[/itex]= -[itex]\hat{I}[/itex], show that |[itex]\Psi[/itex]> is orthogonal to [itex]\hat{A}[/itex]|[itex]\Psi[/itex]>
Homework Equations
I know that [itex]\hat{A}[/itex] can be represented by a unitary operator, [itex]\hat{U}[/itex], and the complex conjugation operator, [itex]\hat{K}[/itex], in the following way [itex]\hat{A}[/itex] = [itex]\hat{U}[/itex][itex]\hat{K}[/itex].
Also from the definition of anti-unitary operator <[itex]\hat{A}[/itex][itex]\Psi[/itex]|[itex]\hat{A}[/itex][itex]\Phi[/itex]> = <[itex]\Psi[/itex]|[itex]\Phi[/itex]>* = <[itex]\Phi[/itex]|[itex]\Phi[/itex]>
The Attempt at a Solution
I've tried starting with the inner product of psi and A*psi, and inserting "identities" of A and A's inverse, but then I realized in both my class and in sakurai, we have not defined the inverse of an anti-unitary operator, and sakurai warns about acting anti-unitary operators on bra's, I think he even says we/he will never do such an operation. So that's when I went to the definition of A being composed of a unitary operator and the complex conjugation operator, but then I get stuck with the inverse of the complex conjugation operator, and I'm not sure if that is even defined?
My thought is to somehow get A^2 into the inner product of psi and Apsi, then I would get a -1 after it acts on the ket, then compare the original inner product, with the final inner product having the minus sign, and declaring that that can't be true, so therefore the inner product is zero...Something along those lines...but...
All these inverses have got me stuck!
Please help.
Thanks.
JP