Preview

PDF, English Download (2MB) | Terms of use

Abstract

Quantum Chromodynamics (QCD) is a rich non-Abelian gauge theory that describes the strong nuclear force. Heavy ion collisions create a QCD plasma, in which the weakly coupled, high-temperature regime of the theory can be studied. At low momenta in QCD plasmas, several features emerge that affect transport phenomena during the thermalization of the plasma. In this thesis we will investigate two such features and explore their manifestations in heavy ion collisions and their significance. The first half of this thesis investigates the dissipative effects of sphaleron transitions in the quark-gluon plasma. We modify the anomalous hydrodynamic equations of motion to account for dissipative effects due to QCD sphaleron transitions. By investigating the linearized hydrodynamic equations, we show that sphaleron transitions lead to nontrivial effects on vector and axial charge transport phenomena in the presence of a magnetic field. Due to the dissipative effects of sphaleron transitions, a wavenumber threshold $k_{\rm CMW}$ emerges characterizing the onset of chiral magnetic waves. Sphaleron damping also significantly impacts the time evolution of both axial and vector charge perturbations in a QCD plasma in the presence of a magnetic field. Based this, we also investigate the dependence of the vector charge separation on the sphaleron transition rate, which may have implications for the experimental search for the Chiral Magnetic Effect in Heavy Ion Collisions. The second half of this thesis explores the formation of a condensate in the moments after a heavy ion collision. We show gauge condensation, which occurs as a consequence of the large density of gluons. To identify this condensation phenomenon, we construct two local gauge-invariant observables that carry the macroscopic zero mode of the gauge condensate. The first order parameter investigated here is the correlator of the spatial Polyakov loop. We also consider, for the first time, the correlator of the gauge invariant scalar field, associated to the exponent of the Polyakov loop. Using real-time lattice simulations of classical-statistical $SU(2)$ gauge theory, we find gauge condensation on a system-size dependent time scale $\tcond\sim L^{1/\zeta}$ with a universal scaling exponent $\zeta$. Furthermore, we suggest an effective theory formulation describing the dynamics using one of the order parameters identified. The formation of a condensate at early times may have intriguing implications for the early stages in heavy ion collisions.