Q6 (Taylor 2.11 ) If the sum of coefficients a + in Eq. (2.8.4) becomes negative, then the F magnetic system will be unstable. Use your answer to Problem 2.10 (25) to find the minimum value that V(N1 N,)/p must have to ensure that the magnet is stable. (Here er is the Fermi energy of the unmagnetized system.) Does your result agree qualitatively with the semiclassical argument that N, - Nq, should be equal to the difference between the integrated densities of states N(&ru)- N(en)? & F1