European Physical Journal C: Particles and Fields (Dec 2021)

Cutting rules on a cylinder: a simplified diagrammatic approach to quantum kinetic theory

  • Tomáš Blažek,
  • Peter Maták

DOI
https://doi.org/10.1140/epjc/s10052-021-09874-3
Journal volume & issue
Vol. 81, no. 12
pp. 1 – 8

Abstract

Read online

Abstract Nonequilibrium quantum field theory is often used to derive an approximation for the evolution of number densities and asymmetries in astroparticle models when a more precise treatment of quantum thermal effects is required. This work presents an alternative framework using the zero-temperature quantum field theory, S-matrix unitarity, and classical Boltzmann equation as starting points leading to a set of rules for calculations of thermal corrections to reaction rates. Statistical factors due to on-shell intermediate states are obtained from the cuts of forward diagrams with multiple spectator lines. It turns out that it is equivalent to cutting closed diagrams on a cylindrical surface.