QFT Propagators

physicsquantum field theoryMatsubaracausalityGreen's functionFeynmancetztikz

Complex plane visualization of different propagator types in quantum field theory: retarded, advanced, and Feynman propagators. The diagram shows their analytic structure in relation to Matsubara frequencies (dots on imaginary axis). This representation helps understanding causality in quantum field theory and the connection between real-time and imaginary-time (thermal) formalisms.