For question 4:
Would it be possible to see the full derivation for the top of the energyband? I think I might get the gist of it, but it would be helpfull to see the full calculation
Dear Iris,
If you found the correct density of states in part 3, then you only need to Taylor expand around \omega=\omega_0. If you do that, do you get the same result as in the solutions?
Thank you for your answer!
Sadly I stilll won’t come to the right answer. I wouldn’t expect a square root of delta(omega) in the denominator. I tried it a couple of times, would it please be possible to see the calculation? 
