Aspects of Non-Equilbrium Quantum Field Theory in Heavy Ion Collisions

In this talk we present results obtained when fluid dynamical fluctuations are included in relativistic $3+1$ dimensional viscous fluid dynamics. We discuss effects of the interactions of fluctuations due to nonlinearities and the cutoff dependence.

The field of relativistic heavy ion physics has seen significant advancement in the new millennium toward a greater understanding of QCD at high temperatures with the commissioning and operation of the Relativistic Heavy Ion Collider. Here we review progress in the field as presented in a set of lectures at the Lake Louise Winter Institute on Fundamental Interactions in February 2004.

Heavy ion collisions at ultrarelativistic energies offer the opportunity to study the irreversibility of multiparticle processes. Together with the many-body decays of resonances, the multiparticle processes cause the system to evolve according to Prigogine's steady states rather than towards statistical equilibrium. These results are general and can be easily checked by any microscopic string-, transport-, or cascade model for heavy ion collisions. The absence of pure equili...

We provide a concise review on recent theory advancements towards full-fledged (3+1)D dynamical descriptions of relativistic nuclear collisions at finite baryon density. Heavy-ion collisions at different collision energies produce strongly-coupled matter and probe the QCD phase transition at the crossover, critical point, and first-order phase transition regions. Dynamical frameworks provide a quantitative tool to extract properties of hot QCD matter and map fireballs to the ...

In this article, we present a concise and self-contained introduction to nonequilibrium statistical mechanics with quantum field theory by considering an ensemble of interacting identical bosons or fermions as an example. Readers are assumed to be familiar with the Matsubara formalism of equilibrium statistical mechanics such as Feynman diagrams, the proper self-energy, and Dyson's equation. The aims are threefold: (i) to explain the fundamentals of nonequilibrium quantum fie...

In these lectures I present the key ideas driving the field of relativistic heavy-ion physics and develop some of the theoretical tools needed for the description and interpretation of heavy-ion collision experiments.

We review recent developments for the description of far-from-equilibrium dynamics of quantum fields and subsequent thermalization.

We review recent developments in the ab-initio theoretical description of the initial state in heavy-ion collisions. We emphasize the importance of fluctuations, both for the phenomenological description of experimental data from the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC), and the theoretical understanding of the non-equilibrium early time dynamics and thermalization of the medium.

We investigate the conditions under which particle multiplicities in high energy collisions are Boltzmann distributed, as is the case for hadron production in e^+e^-, pp, p-pbar and heavy ion collisions. We show that the apparent temperature governing this distribution does not necessarily imply equilibrium (thermal or chemical) in the usual sense, as we explain. We discuss an explicit example using tree level amplitudes for N photon production in which a Boltzmann-like distr...

We review the theoretical aspects relevant in the description of high energy heavy ion collisions, with an emphasis on the learnings about the underlying QCD phenomena that have emerged from these collisions.