: Uses periodic (for bosons) or anti-periodic (for fermions) boundary conditions in Euclidean time ( Real-Time Formalism
: Used for calculating dynamical quantities and spectral functions, this method utilizes complex-time contours (like the Schwinger-Keldysh contour) to describe non-equilibrium or time-dependent processes.
The book is structured into two primary sections that transition from foundational principles to advanced applications:
who have a prior foundation in standard quantum field theory and statistical mechanics. Google Books Thermal Field Theory - Cambridge University Press