Date of Completion
Gerald V. Dunne
Field of Study
Doctor of Philosophy
In this dissertation we study semi-classical effects in Quantum Field Theory (QFT) and made use of the universal behavior of the asymptotic expansions to study of quantum non-equilibrium dynamics. We consider the evolution of quantum field theoretical systems subject to a time-dependent perturbation and demonstrate a universal form to the adiabatic particle number, corresponding to optimal truncation of the (divergent and asymptotic) adiabatic expansion. In this optimal basis, the particle number number evolves smoothly in time according to the universal smoothing of adiabatic evolution in the Stokes Phenomenon, thus providing a well-defined notion for evolution through a non-equilibrium process. The optimal basis also clearly illustrates interference effects associated with particle production for sequences of pulses in Schwinger and de Sitter particle production. We also demonstrate the basis dependence of the adiabatic particle number across several equivalent approaches, which revealed that particle production is a measure of small deviations between the exact and adiabatic solutions of the Ermakov-Milne equation for the associated time-dependent oscillators. Given a consistent formulation of the optimal time-dependent particle number, led us to explore the consequences for the back-reaction mechanism in particle production and provide a modification of Jarzynski's non-equilibrium work theorem to study non-equilibrium physics under adiabatic evolution. Lastly, we classify semiclassical saddle point (non-instanton) solutions in the asymptotically free CP(N-1) model in QFT.
Dabrowski, Robert, "Adiabatic Expansion in Quantum Field Theory and Quantum Non-equilibrium Dynamics" (2017). Doctoral Dissertations. 1513.