From its inception in statistical physics to its role in the construction and in the development of the asymmetric Yang–Mills phase in quantum field theory, the notion of spontaneous broken symmetry permeates contemporary physics. This is reviewed with particular emphasis on the conceptual issues.
When studying thermodynamic properties by means of quantum field theory methods one can deform the Matsubara integration contour in the complex time plane. The deformations are restricted by Hamiltonian singularities which are due to turning on an interaction. One should construct the real-time technique in the true vacuum taking the interaction into account.
Broken Symmetry and Yang–Mills Theory
