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Simple problem on expectation value

  1. Mar 16, 2012 #1
    I know that <Aψ|Aψ> = <A2>. Can anyone tell please tell me how you get one line to the another?
  2. jcsd
  3. Mar 16, 2012 #2
    Ok so, <Aψ|Aψ> = <AAψ|ψ> because A is self adjoint (hermitian). What next?
  4. Mar 16, 2012 #3
    [tex]\langle A\psi \mid A\psi \rangle = \langle \psi \mid A^{\dagger}A\mid \psi \rangle[/tex]

    If A is Hermintian:

    [tex] \langle \psi \mid A^{\dagger}A\mid \psi \rangle = \langle \psi \mid A^{2}\mid \psi \rangle [/tex]

    And that's it :)
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