Speaker: David Wagner (Goethe-Universität Frankfurt am Main)

Title: Inverse-Reynolds Dominance approach to transient fluid dynamics


Speaker: Victor E. Ambruș (Universitatea de Vest Din Timisoara)

Title: Applicability of hydrodynamics in relativistic heavy-ion collisions

Date: 3 April 2023, 11:00

Place: Building 3. Meeting Room



Inverse-Reynolds Dominance approach to transient fluid dynamics: We consider the evolution equations for the bulk viscous pressure, diffusion current and shear tensor derived within the second order relativistic dissipative hydrodynamics from kinetic theory. By matching the irreducible moments of the single-particle distribution function to the dissipative quantities, we obtain relaxation-type equations featuring a number of transport coefficients, which can be calculated to arbitrary precision. In the case of hard-sphere interactions, the values of these transport coefficients are compatible with the second law of thermodynamics.

Applicability of hydrodynamics in relativistic heavy-ion collisions: This talk focuses on the comparison between the predictions of relativistic hydrodynamics and kinetic theory for flow observables in the context of heavy-ion collisions. While the two theories agree for systems which are close to equilibrium (after hydrodynamization), their far-from-equilibrium behaviours differ considerably (during preequilibrium). An analysis of the early-time Bjorken flow attractor in the two theories reveals that discrepancies during the (short) preequilibrium evolution leads to significant discrepancies in flow observables. As a workaround, we propose a rescaling of the initial conditions for hydrodynamics that compensate for the differences in the early-stage dynamics, which brings (ideal and viscous) hydrodynamics in agreement with kinetic theory provided that the equilibration time scale is shorter than the time scale associated to transverse expansion (typically the system size, R).