ABSTRACT
The unitarity condition on the scattering matrix, derived in Chapter 7, leads to a relation known as the optical theorem which connects the amplitudes of real and virtual processes. If we write S = 1 + i T , $$ \begin{aligned} S={ \mathbb 1 }+iT \ , \end{aligned} $$ https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315369723/48d43afe-85b0-4e2b-a932-df2bd1af07be/content/math16_751.tif"/>
