Ok, so basically I inserted the Fourier representation of the energy factors into eq. (3.5.3) and came up with a factor of $$e^(iE_a * t) * V_(by)*V_(ya) * e^(-iE_y * t)$$ within the two integrals and I thought maybe I could get V(t) somewhere through that and the rest of my work has to do with...
Homework Statement
Basically I wanted to see if anyone would be willing to give me the solution to the 4th problem of the Weinberg textbook on quantum field theory. The exact question in the book is "Derive the perturbation expansion (3.5.8) directly from the expansion (3.5.3) of old-fashioned...