In this thesis, we develop a perturbative formulation of nonequilibrium thermalquantum field theory, capable of describing the evolution of both temporal and spatial inhomogeneities in relativistic, quantumstatistical ensembles. We begin with areview of the necessary prerequisites from classical thermodynamics, classical andquantum statistical mechanics, quantum field theory and equilibrium thermal fieldtheory. Setting general boundary conditions on the ensemble expectation values ofproducts of interactionpicture creation and annihilation operators, we derive freepropagators in which spacetime translational invariance is explicitly broken. Bymeans of the SchwingerKelydsh, closedtime path formalism, we are then able tointroduce a pathintegral description that accounts consistently for these temporaland spatial inhomogeneities. Subsequently, we develop a timedependent perturbation theory that is free of the pathologies previously thought to spoil such approachesto nonequilibrium dynamics.Following an unambiguous definition of the number density of particles, wederive from first principles perturbative, fieldtheoretic evolution equations for statistical distribution functions. These evolution equations do not rely on the gradientexpansion of socalled Wigner functions, as is necessary in the alternative KadanoffBaym approach, and are consistent with the wellknown Boltzmann equations inthe classical limit. Finally, with reference to a simple toy model, we highlight theappearance of processes otherwise kinematically disallowed in existing approachesto thermal field theory. These evanescent contributions are a consequence of themicroscopic violation of energy conservation and are shown to be significant to theearlytime evolution of nonequilibrium systems. We observe that the spectral evolution oscillates with timedependent frequencies, which is interpreted as a signal ofnonMarkovian, memory effects.
Date of Award  31 Dec 2012 

Original language  English 

Awarding Institution   The University of Manchester


Supervisor  Apostolos Pilaftsis (Supervisor) 

 nonequilibrium thermal quantum field theory
Thermal Quantum Field Theory and Perturbative NonEquilibrium Dynamics
Millington, P. (Author). 31 Dec 2012
Student thesis: Phd