H. Niemi

Derivation of transient relativistic fluid dynamics from the Boltzmann equation

In this work we present a general derivation of relativistic fluid dynamics from the Boltzmann equation using the method of moments. The main difference between our approach and the traditional 14-moment approximation is that we will not close the fluid-dynamical equations of motion by truncating the expansion of the distribution function. Instead, we keep all terms in the moment expansion. The reduction of the degrees of freedom is done by identifying the microscopic time scales of the Boltzmann equation and considering only the slowest ones. In addition, the equations of motion for the dissipative quantities are truncated according to a systematic power-counting scheme in Knudsen and inverse Reynolds number. We conclude that the equations of motion can be closed in terms of only 14 dynamical variables, as long as we only keep terms of second order in Knudsen and/or inverse Reynolds number. We show that, even though the equations of motion are closed in terms of these 14 fields, the transport coefficients c information about all the moments of the distribution function. In this way, we can show that the particle-diffusion and shear-viscosity coefficients agree with the values given by the Chapman-Enskog expansion. PACS numbers:

Event-by-event distributions of azimuthal asymmetries in ultrarelativistic heavy-ion collisions

Relativistic dissipative fluid dynamics is a common tool to describe the space-time evolution of the strongly interacting matter created in ultrarelativistic heavy-ion collisions. For a proper comparison to experimental data, fluid-dynamical calculations have to be performed on an event-by-event basis. Therefore, fluid dynamics should be able to reproduce, not only the event-averaged momentum anisotropies, 〈vn〉, but also their distributions. In this paper, we investigate the event-by-event distributions of the initial-state and momentum anisotropies en and vn, and their correlations. We demonstrate that the event-by-event distributions of relative vn fluctuations are almost equal to the event-by-event distributions of corresponding en fluctuations, allowing experimental determination of the relative anisotropy fluctuations of the initial state. Furthermore, the correlation c(v2,v4) turns out to be sensitive to the viscosity of the fluid providing an additional constraint to the properties of the strongly interacting matter.

Influence of a temperature-dependent shear viscosity on the azimuthal asymmetries of transverse momentum spectra in ultrarelativistic heavy-ion collisions

We study the influence of a temperature-dependent shear viscosity over entropy density ratio

Transition from ideal to viscous Mach cones in a kinetic transport approach

\eta/s

Elliptic flow in nuclear collisions at ultrarelativistic energies available at the CERN Large Hadron Collider

, different shear relaxation times

Transverse spectra of hadrons at RHIC

\tau_\pi

Derivation of transient relativistic fluid dynamics from the Boltzmann equation for a multi-component system

, as well as different initial conditions on the transverse momentum spectra of charged hadrons and identified particles. We investigate the azimuthal flow asymmetries as a function of both collision energy and centrality. The elliptic flow coefficient turns out to be dominated by the hadronic viscosity at RHIC energies. Only at higher collision energies the impact of the viscosity in the QGP phase is visible in the flow asymmetries. Nevertheless, the shear viscosity near the QCD transition region has the largest impact on the collective flow of the system. We also find that the centrality dependence of the elliptic flow is sensitive to the temperature dependence of

Dynamical freeze-out condition in ultrarelativistic heavy ion collisions

\eta/s

Transition From Ideal To Viscous Mach Cones In A Partonic Transport Model

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Erratum: Derivation of transient relativistic fluid dynamics from the Boltzmann equation [Phys. Rev. D85, 114047 (2012)]

Abstract Using a microscopic transport model we investigate the evolution of conical structures originating from the supersonic projectile moving through the hot matter of ultrarelativistic particles. Using different scenarios for the interaction between projectile and matter, and different transport properties of the matter, we study the formation and structure of Mach cones. Especially, a dependence of the Mach cone angle on the details and rate of the energy deposition from projectile to the matter is investigated. Furthermore, the two-particle correlations extracted from the numerical calculations are compared to an analytical approximation. We find that the propagation of a high energetic particle through the matter does not lead to the appearance of a double peak structure as observed in the ultrarelativistic heavy-ion collision experiments. The reason is the strongly forward-peaked energy and momentum deposition in the head shock region. In addition, by adjusting the cross section we investigate the influence of the viscosity to the structure of Mach cones. A clear and unavoidable smearing of the profile depending on a finite ratio of shear viscosity to entropy density is clearly visible.