Hydrodynamic description of the baryon-charged quark-gluon plasma

Abstract

One of the primary goals of nuclear physics is studying the phase diagram of Quantum Chromodynamics, where a hypothetical critical point serves as a landmark. A systematic model-data comparison of heavy-ion collisions at center-of-mass energies between 1 and 100 GeV per nucleon is essential for locating the critical point and the phase boundary between the deconfined quark-gluon plasma and the confined hadron resonance gas. At these energies the net baryon density of the system can be high and critical fluctuations can become essential in the presence of the critical point. Simulating their dynamical evolution thus becomes an indispensable part of theoretical modeling.In this thesis we first present the (3+1)-dimensional relativistic hydrodynamic code BEShydro, which solves the equations of motion of second-order Denicol-Niemi-Molnar-Rischke theory, including bulk and shear viscous components as well as baryon diffusion current. We then study the effects caused by the baryon diffusion on the longitudinal dynamics and on the phase diagram trajectories of fluid cells at different space-time rapidities of the system, and how they are affected by critical dynamics near the critical point. We finally explore the evolution of non-hydrodynamic slow processes describing long wavelength critical fluctuations near the critical point, by extending the conventional hydrodynamic description by coupling it to additional explicitly evolving slow modes, and their back-reaction to the bulk matter properties.

Baryon diffusion near the QCD critical point

“…In Fig. 3 we show analogous effects on the phase diagram trajectories caused by (a) the shear stress tensor and (b) the bulk viscous pressure Π, separately (easily achievable as BES features a modular structure that allows to turn on and off different dissipative components and study their physical effects individually [16]). We use the same setup as above, setting = 0 = Π initially.…”

Baryon diffusion near the QCD critical point

“…In Fig. 3 we show analogous effects on the phase diagram trajectories caused by (a) the shear stress tensor π µν and (b) the bulk viscous pressure Π, separately (easily achievable as BESHYDRO features a modular structure that allows to turn on and off different dissipative components and study their physical effects individually [16]). We use the same setup as above, setting π µν = 0 = Π initially.…”

Baryon-charged medium response to energetic partons

“…[22,23] (see also Chapter 5 of Ref. [24]) to which we refer the reader for additional details. Gubser flow describes longitudinally boost-invariant and azimuthally symmetric transverse expansion of a conformal system that appears static when expressed in the curvilinear Gubser coordinates parametrizing de Sitter space [20,21].…”

“…The azimuthal angle φp associated with the momentum of an emitted particle should be distinguished from its spatial counterpart φ ≡ arctan(x/y) for the azimuthal position of a fluid cell in coordinate space. 10 Validations of the BEShydro + iS3D framework using a setup similar to the one here can be found in L. Du's Ph.D. thesis [24].…”