Strong dissipative behavior in quantum field theory - art. no. 123508

We study the conditions under which an overdamped regime can be attained in the dynamic evolution of a quantum field configuration. Using a real-time formulation of finite temperature field theory, we compute the effective ev olution equation of a scalar field configuration, quadratically interacting with a given set of other scalar fields. We then show that, in the overdam ped regime, the dissipative kernel in the field equation of motion is close ly related to the shear viscosity coefficient, as computed in scalar field theory at finite temperature. The effective dynamics is equivalent to a tim e-dependent Ginzburg-Landau description of the approach to equilibrium in p henomenological theories of phase transitions. Applications of our results, including a recently proposed inflationary scenario called "warm inflation ," are discussed. [S0556-2821(98)03474-5].