Controlled nonperturbative dynamics of quantum fields out-of-equilibrium
May, 200148 pages
Published in:
- Nucl.Phys.A 699 (2002) 847-886
e-Print:
- hep-ph/0105311 [hep-ph]
Report number:
- HD-THEP-01-26
Citations per year
Abstract:
We compute the nonequilibrium real-time evolution of an O(N)-symmetric scalar quantum field theory from a systematic 1/N expansion of the 2PI effective action to next-to-leading order, which includes scattering and memory effects. In contrast to the standard 1/N expansion of the 1PI effective action, the next-to-leading order expansion in presence of a possible expectation value for the composite operator leads to a bounded time evolution where the truncation error may be controlled by higher powers in 1/N. We present a detailed comparison with the leading-order results and determine the range of validity of standard mean field type approximations. We investigate ``quench'' and ``tsunami'' initial conditions frequently used to mimic idealized far-from-equilibrium pion dynamics in the context of heavy-ion collisions. For spatially homogeneous initial conditions we find three generic regimes, characterized by an early-time exponential damping, a parametrically slow (power-law) behavior at intermediate times, and a late-time exponential approach to thermal equilibrium. The different time scales are obtained from a numerical solution of the time-reversal invariant equations in 1+1 dimensions without further approximations. We discuss in detail the out-of-equilibrium behavior of the nontrivial n-point correlation functions as well as the evolution of a particle number distribution and inverse slope parameter.Note:
- 48 pages, 20 figures, Nucl.Phys.A version, minor wording changes, reference added
- field theory: scalar
- symmetry: O(N)
- nonperturbative
- expansion 1/N
- effective action
- mean field approximation
- boundary condition
- symmetry: chiral
- numerical calculations
References(51)
Figures(20)