Many particle physics - Hamiltonian for Fermi system

Plaetean
Messages
35
Reaction score
0

Homework Statement


Working through problems in Mahan's 'Many Particle Physics' book, and at the end of the 1st chapter there's a question where we're asked to consider a fermion system with three energy states with eigenvalues E1, E2, E3, and matrix elements M12, M23, M13 which connect them and allow transitions between them.

The question asks us to write down a Hamiltonian for the system in terms of creation and annihilation operators, and then determine the eigenvalues for the system.

Homework Equations

The Attempt at a Solution


I'm really a bit lost as to where to start for this, and all I can really think of doing is writing the standard Hamiltonian for a quantum SHO as a sum over states, but I'm not confident this is remotely right.
<br /> H=\hbar\sum_{n=1}^{3}\omega_n(a_n^\dagger a_n + \frac{1}{2})+M_{12}+M_{23}+M_{13}<br />

Is it the case that the energy eigenvalues will just be E1, E2 and E3, as the fact that transitions can occur doesn't change the actual eigenvalues of the system?

Thanks as always!
 
Physics news on Phys.org
Bump!
 
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