A famous toy model in quantum field theory is the scalar {D3 theory. The only field

in the theory is a neutral scalar (spinâ€”zero) particle, which is represented by a line

without an arrow, and the only vertex in the theory is where three scalar lines meet. (a) Draw all the leading-order Feynman diagrams for the elastic scattering of two

such scalars. As before, label the external momenta to help you make sure that

you obtain all of the diagrams. (b) Now do the same for the process of one scalar decaying into three scalars. Which

of these two processes [(a) or (b)] has more independent diagrams? Science