Derive the general variational principle for the theory of piez... | Filo

Variational Principle. The energy of a system with wave functio... | Filo

(a) Use the variational principle to prove that first-order non-degenerate perturbation theory always overestimates (or at any rate never underestimates the ground state energy. (b) In view of (a), you would expect that the second-order correction to the ground state is always negative. Confirm that this is indeed the case, by examining Equation 7.15. | Numerade