PUB - Publikationen an der Universität Bielefeld

Non-equilibrium Green’s functions are an efficient method in order to describe the pre- equilibrium evolution of early stages in heavy-ion collisions. With them we are also able to discuss at which point hydrodynamics becomes applicable in such systems. In a recent study the Green’s functions for the energy-momentum tensor for transverse perturbations on top of a homogeneous background were obtained by considering moments of the distribution function. We will extend this formalism and include conserved charges. Within kinetic theory in relaxation time approximation we will study the pre-equilibrium evolution of the homogeneous background for non-vanishing initial charge densities and compute the Green’s functions for the charge current for initial charge perturbations around zero density on top of the background. For the background we discuss the evolution from the early time free-streaming behaviour to the regime of viscous hydrodynamics. For the perturbations we will consider the evolution in terms of Green’s functions and show which response functions will survive when the system enters the hydrodynamic regime.

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Universität Bielefeld, Master Thesis, 2021