Show How to Write A as B + iC: Hermitian Operators

In summary, a Hermitian operator is a linear operator used in quantum mechanics that is equal to its own conjugate transpose. It is important to know how to write an operator as a sum of two parts, with one part being the Hermitian conjugate of the other, in order to easily determine eigenvalues and eigenvectors. The imaginary unit (i) in the expression for a Hermitian operator represents the complex nature of quantum mechanics and ensures that the operator is self-adjoint. To show that an operator is Hermitian, we can use the equation A = A<sup>&#8224;</sup>. Any operator can be written as a sum of a Hermitian and anti-Hermitian operator
  • #1
Dragonfall
1,030
4
How do I show that an arbitrary operator A can be writte as A = B + iC where B and C are hermitian?
 
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  • #2
Rewrite A as follows:

[tex]A = \frac{(A+A^{\dagger})}{2} + \frac{(A-A^{\dagger})}{2}[/tex]

Do you see why you can write A like that?
And can you carry on?
 
Last edited:
  • #3
anytime anywhere you have an involution J you can alwaYS WRiTE ANYTHIng AS

x = (x+JX)/2 + (X-JX)/2,

where X+JX is invariant under J, and X-JX is anti-invariant under J.

this is what lies beneath this fact.
 

Related to Show How to Write A as B + iC: Hermitian Operators

What is a Hermitian operator?

A Hermitian operator is a mathematical concept used in quantum mechanics. It is a linear operator that has the property of being equal to its own conjugate transpose. This means that the operator and its conjugate transpose have the same matrix elements, or in other words, they are symmetric.

Why is it important to know how to write an operator as a sum of two parts?

Writing an operator as a sum of two parts, where one part is the Hermitian conjugate of the other, is important because it allows us to easily determine the eigenvalues and eigenvectors of the operator. This is crucial in solving quantum mechanical problems and understanding the behavior of quantum systems.

What is the significance of the imaginary unit (i) in the expression for a Hermitian operator?

The imaginary unit (i) in the expression for a Hermitian operator represents the complex nature of quantum mechanics. It is used to ensure that the operator is self-adjoint, meaning that it is equal to its own adjoint. This is necessary for the operator to have real eigenvalues, which are essential in calculating physical quantities in quantum mechanics.

How do you show that an operator is Hermitian?

To show that an operator is Hermitian, we can use the following equation: A = A, where A is the operator and A is its conjugate transpose. This means that the matrix elements of the operator and its conjugate transpose are equal. If this equation holds true, then the operator is Hermitian.

Can any operator be written as a sum of a Hermitian and anti-Hermitian operator?

Yes, any operator can be written as a sum of a Hermitian and anti-Hermitian operator. This is known as the decomposition of operators. The Hermitian part represents the physical properties of the operator, while the anti-Hermitian part is related to the time evolution of the system. This decomposition is useful in simplifying the calculations involved in solving quantum mechanical problems.

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