(a) Show that the Lorentz invariant Lagrangian (in the sense of Section 12.1B)
L=−2mUαUα−cqUαAα
gives the correct relativistic equations of motion for a particle of mass m and charge q interacting with an external field described by the 4-vector potential Aα(x).
(b) Define the canonical momenta and write out the effective Hamiltonian in both covariant and space-time form. The effective Hamiltonian is a Lorentz invariant. What is its value?