Speaker: Eric Toombs
Title: Going blue. Source terms, scattering, and causality in QM and QFT

Abstract:
The Schrödinger equation is modified. A source term is added, making it inhomogeneous. An unphysical decay is also added. The result is called the blue equation because “inhomogeneous Schrödinger equation” is too long. This allows for time Fourier transforms, simplifies scattering theory, allows for scattering theory with normalised states, and explains the (unnormalised) in and out “states” of the Lippmann-Schwinger equation. Implications for the S matrix are considered.
The source term is considered as a physical quantity of its own. It reveals a causal nature which was hidden or absent before.
Time-permitting, applications of sources to quantum field theory are considered. An inhomogeneous Klein-Gordon equation is used to reveal the effect of special relativity on causality.