How Do You Determine if an Operator is Unitary, Hermitian, or a Projector?

  • Thread starter Thread starter MrRobot
  • Start date Start date
  • Tags Tags
    Complex Operator
MrRobot
Messages
5
Reaction score
0

Homework Statement


Hi, so I have been given the following operator in terms of 3 orthonormal states |Φi>

A = |Φ2><Φ2| + |Φ3><Φ3| - i|Φ1><Φ2| - |Φ1><Φ3| + i|Φ2><Φ1| - |Φ3><Φ1|
So I need to determine whether A is unitary and/or Hermitian and/or a projector and then calculate the eigenvalues and eigenfunctions in the |Φi> basis.

The second question is to find eigenvalues and eigenfunctions of the complex conjugation operator acting on complex functions, Cα(x) = α*(x)

Homework Equations

The Attempt at a Solution


So for the first one I said it is an operator because, it cannot be unitary since AAτ ≠ unit matrix and not hermitian since A ≠ A, but now I fail to show A2 = A in order to prove that it is actually a projector. please help if there is an easier way.

The second part of the question am just failing to use that A in the formula A|Φi> = a|Φi> to find the eigenvalues and eigenfunctions.

The second question I don't know where to even start.
Please help, thank you very much.
 
Physics news on Phys.org
MrRobot said:
but now I fail to show A2 = A in order to prove that it is actually a projector. please help if there is an easier way.
Please provide your actual attempt.

MrRobot said:
The second question I don't know where to even start.
What is the definition of an eigenfunction? How does complex conjugation act on a general complex function?
 
Thread 'Need help understanding this figure on energy levels'
This figure is from "Introduction to Quantum Mechanics" by Griffiths (3rd edition). It is available to download. It is from page 142. I am hoping the usual people on this site will give me a hand understanding what is going on in the figure. After the equation (4.50) it says "It is customary to introduce the principal quantum number, ##n##, which simply orders the allowed energies, starting with 1 for the ground state. (see the figure)" I still don't understand the figure :( Here is...
Thread 'Understanding how to "tack on" the time wiggle factor'
The last problem I posted on QM made it into advanced homework help, that is why I am putting it here. I am sorry for any hassle imposed on the moderators by myself. Part (a) is quite easy. We get $$\sigma_1 = 2\lambda, \mathbf{v}_1 = \begin{pmatrix} 0 \\ 0 \\ 1 \end{pmatrix} \sigma_2 = \lambda, \mathbf{v}_2 = \begin{pmatrix} 1/\sqrt{2} \\ 1/\sqrt{2} \\ 0 \end{pmatrix} \sigma_3 = -\lambda, \mathbf{v}_3 = \begin{pmatrix} 1/\sqrt{2} \\ -1/\sqrt{2} \\ 0 \end{pmatrix} $$ There are two ways...
Back
Top