Proving Orthogonality of Eigenfunctions for Hermitian Operators

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SUMMARY

The eigenfunctions of a Hermitian operator are orthogonal when corresponding to different eigenvalues. This is established by considering a Hermitian operator O with eigenfunctions |a1> and |a2>, associated with eigenvalues a1 and a2. By manipulating the equations O|a1>=a1|a1> and O|a2>=a2|a2>, and subtracting the resulting expressions for , one can demonstrate the orthogonality of the eigenfunctions. Additionally, it is crucial to note that the eigenvalues of Hermitian operators are real.

PREREQUISITES
  • Understanding of Hermitian operators in quantum mechanics
  • Familiarity with eigenvalues and eigenfunctions
  • Knowledge of linear algebra concepts, particularly inner products
  • Basic grasp of quantum mechanics principles
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  • Learn about the spectral theorem for Hermitian operators
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Hi there,

Was wondering if anyone could point me in the right direction for this one?

Show that the eigenfunctions of a Hermitian operator corresponding to different eigenvalues are orthogonal?

Thanks
 
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Alright, say you have an hermitian operator, O with eigenfunctions |a1> and |a2>, with eigenvalues of a1 and a2 respectively. Then:
O|a1>=a1|a1> (1)
<a1|O=a1*<a1| (2)
O|a2>=a2|a2> (3)
and
<a2|O=a2*<a2| (4)
Now right multiply |a1> in equation (4) and left multiply by <a2| in equation (1) to get two expressions for <a2|O|a1>. Subtract the two equations and observe.
-edit: keep in mind that the eigenvalues of hermitian operators are real. You can prove this by letting a1=a2
 
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