Is G Hermitian Given H and K Definitions?

Hermitian.In summary, the conversation discusses the properties of an operator G on a Hilbert Space, where it is shown that (a) H = 1/2 (G + G^{\dagger}) and (b) K = -1/2 (G - G^{\dagger}) are both Hermitian. However, there is a discrepancy in (b) as the operator given appears to be anti-Hermitian, leading to doubts about the correctness of (c) which uses this incorrect result. It is suggested that a change in definition or a condition for G is needed to solve the equations. Alternatively, if K is defined as -i/2(...), then it is shown to be
  • #1
sgoodrow
12
0
1. Let G be an operator on H (Hilbert Space). Show that:
(a) H = 1/2 (G + G[tex]^{\dagger}[/tex]) is Hermitian.
(b) K = -1/2 (G - G[tex]^{\dagger}[/tex]) is Hermitian.
(c) G = H + iK
.

Homework Equations


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3. The Attempt at a Solution :

(a) Since the adjoint of the sum of two operators does not change their position (addition of operators is commutative), it is very straight forward.

(b) This is where I run into trouble, and I think it is because the problem is wrong. The operator given appears to be anti-hermitian (skew-hermitian), however I would like confirmation. This result makes (c) very difficult, as it uses an incorrect answer. My suspicion is that the intended question includes an i (as in, H = -i/2 (...)):

K[tex]^{\dagger}[/tex] = -1/2 (G[tex]^{\dagger}[/tex] - G) = 1/2 (G - G[tex]^{\dagger}[/tex]) = -K.

(c) Well if I am correct about (b), (c) is wrong. I was just hoping someone could confirm I am right, or show me how K is Hermitian. I can take it from there.
 
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  • #2
If the problem should be as stated this will give a condition for G that allows to solve all equations.
If G is arbitrary and the equations should be satisfied for general G there has to be a change in definition.
K= -i/2(...)
 

FAQ: Is G Hermitian Given H and K Definitions?

What does it mean for an operator to be Hermitian?

A Hermitian operator is one that is equal to its own conjugate transpose. In other words, if A is a Hermitian operator, then A=A†, where † represents the conjugate transpose operation. This property is important in quantum mechanics, as it ensures that the operator's eigenvalues are real and that its eigenvectors are orthogonal to each other.

How do you determine if an operator is Hermitian?

To determine if an operator is Hermitian, you need to check if it satisfies the condition A=A†. This can be done by taking the complex conjugate of the operator and then transposing it. If the resulting matrix is equal to the original operator, then it is Hermitian.

What is the significance of a Hermitian operator in quantum mechanics?

Hermitian operators are important in quantum mechanics because they represent measurable physical observables, such as position, momentum, and energy. The fact that they are equal to their own conjugate transpose ensures that their eigenvalues are real, which correspond to the possible outcomes of a measurement.

Can a non-Hermitian operator have real eigenvalues?

No, a non-Hermitian operator cannot have real eigenvalues. This is because the eigenvalues of a non-Hermitian operator are complex and cannot represent physical observables. Only Hermitian operators have real eigenvalues, which correspond to measurable physical quantities.

Are all physical observables represented by Hermitian operators?

In quantum mechanics, all physical observables are represented by Hermitian operators. However, in classical mechanics, not all physical observables are represented by Hermitian operators. This is because classical mechanics does not involve the concept of superposition, which is necessary for the use of Hermitian operators in quantum mechanics.

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