Abstract:
The idea behind the dispersion relation is as follows: A Physically significant function such as the scattering amplitude is considered, which is in general a function of the real variable k(momentum) and 'theta' (the scattering angle). The first step consists in analytically continuing the function to complex values of its argument. Then it is proceeded to determine its analytic behaviour from the general structure of the underlying theory and the singularities are given a physical interpretation. Cauchy's theorem is invoked to express these analytic properties in a compact form. The resulting mathematical expression is dispersion relation.
