Really, a 4\times4 matrix? If there are 4 base states, why can't I use a 2\times2 matrix? 4 states fit into a 2\times2 matrix, right? I tried this and calculated 2 eigenvalues, \lambda, but I am not sure, if the result is correct, since it "looks" to complicated (see my 1st reply)
Homework Statement Consider two Ising spins coupled together
−βH = h(σ1 + σ2) + Kσ1σ2,
where σ1 and σ2 commute and each independently takes on the values ±1.
What are the eigenvalues of this Hamiltonian? What are the degeneracies of the states?
The Attempt at a Solution Four possible...