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will.c
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I know this is a common and important fact, so I've been willing to accept it, but this has always been something that has been "outside the scope" of my quantum lectures. Does anyone have reference for a proof?
will.c said:I know this is a common and important fact, so I've been willing to accept it, but this has always been something that has been "outside the scope" of my quantum lectures. Does anyone have reference for a proof?
A self-adjoint operator is a linear operator that is equal to its own adjoint. In other words, the operator and its adjoint produce the same result when applied to a given function.
Eigenfunctions are special functions that, when operated on by a linear operator, produce a scalar multiple of themselves. In other words, the operator does not change the form of the function, but only scales it by a constant factor.
This property is important because it allows us to express any function in terms of a linear combination of the eigenfunctions, making it easier to analyze and solve problems involving the operator.
A set of functions is complete if it can represent any function in the given domain. In other words, no function in the domain is left out and every function can be expressed as a combination of the functions in the set.
The spectral theorem states that for a self-adjoint operator, there exists a complete set of eigenfunctions that can be used as a basis for the function space. Therefore, the completeness of the eigenfunctions is a necessary condition for the spectral theorem to hold.