(As an explicit example of the method developed in Problem 7.15, consider an electron at...

(As an explicit example of the method developed in Problem 7.15, consider an electron at rest in a uniform magnetic field , for which the Hamiltonian is (Equation 4.158):

The eigenspinors, , and the corresponding energies, are given in Equation 4.161. Now we turn on a perturbation, in the form of a uniform field in the x direction:

(a) Find the matrix elements of H', and confirm that they have the structure of Equation 735. What is h?

(b) Using your result in Problem 7.15(b), find the new ground state energy, in second-order perturbation theory.

(c) Using your result in Problem 7.15(c), find the variational principle bound on the ground state energy.