Ph. Mota

Effect of bulk viscosity on elliptic flow near the QCD phase transition

In this work, we examine the effect of bulk viscosity on elliptic flow, taking into account the critical behavior of the equation of state and transport coefficients near the QCD phase transition. We found that the p{sub T} dependence of v{sub 2} is quantitatively changed by the presence of the QCD phase transition. Within reasonable values of the transport coefficients, v{sub 2} decreases by a factor of 15% at small p{sub T} values ( 2 GeV), the interplay between the velocity of sound and transport coefficient near the QCD phase transition enhances v{sub 2}. We point out that Grads 14-moment approximation cannot be applied for the calculation of the one-particle distribution function at the freeze-out.

Stability and Causality in relativistic dissipative hydrodynamics

The stability and causality of the Landau–Lifshitz theory and the Israel–Stewart-type causal dissipative hydrodynamics are discussed. We show that the problems of acausality and instability are correlated in relativistic dissipative hydrodynamics and instability is induced by acausality. We further discuss the stability of the scaling solution. The scaling solution of the causal dissipative hydrodynamics can be unstable against inhomogeneous perturbations.

Relativistic dissipative hydrodynamics: A minimal causal theory

We present a new formalism for the theory of relativistic dissipative hydrodynamics. Here, we look for the minimal structure of such a theory which satisfies the covariance and causality by introducing the memory effect in irreversible currents. Our theory has a much simpler structure and thus has several advantages for practical purposes compared to the Israel-Stewart theory (IS). It can readily be applied to the full three-dimensional hydrodynamical calculations. We apply our formalism to the Bjorken model and the results are shown to be analogous to the IS.

Extensivity of irreversible current and stability in causal dissipative hydrodynamics

We extended our formulation of causal dissipative hydrodynamics (Koide et al 2007 Phys. Rev. C 75 034909) to be applicable to the ultra-relativistic regime by considering the extensiveness of irreversible currents. The new equation has a nonlinear term which suppresses the effect of viscosity. We found that such a term is essential to guarantee the positive definiteness of the inertia term and to stabilize numerical calculations in ultra-relativistic initial conditions. Because of the suppression of the viscosity, the behavior of the fluid is more close to that of the ideal fluid. Our result is essentially the same as that from the extended irreversible thermodynamics, but is different from the Israel–Stewart theory. A possible origin of the difference is discussed.

Shock propagation and stability in causal dissipative hydrodynamics

We studied shock propagation and its stability with causal dissipative hydrodynamics in (

Causal Theory of Relativistic Dissipative Hydrodynamics

1+1

Bulk viscosity effects on elliptic flow

)-dimensional systems. We show that the presence of the usual viscosity is not enough to stabilize the solution. This problem is solved by introducing an additional viscosity that is related to the coarse-grain scale of the theory.

New formulation of causal dissipative hydrodynamics: shock wave propagation

We present a new formalism for the theory of relativistic dissipative hydrodynamics, where covariance and causality are satisfied by introducing the memory effect in irreversible currents. Our theory has a much simpler structure and thus has several advantages for practical purposes compared to the Israel-Stewart theory (IS). We apply our formalism to the Bjorken model and the results are shown to be analogous to the IS.

The Landau initial condition and the role of viscosity in relativistic heavy-ion collisions

Abstract The effects of bulk viscosity on the elliptic flow ν 2 are studied using realistic equation of state and realistic transport coefficients. We find that the bulk viscosity acts in a non trivial manner on ν 2 . At low p T , the reduction of ν 2 is even more effective compared to the case of shear viscosity, whereas at high p T , an enhancement of ν 2 compared to the ideal case is observed. We argue that this is caused by the competition of the critical behavior of the equation of state and the transport coefficients.

Effects of expansion and equation of state on the conical propagation in the QGP

The first 3D calculation of shock wave propagation in a homogeneous QGP has been performed within the new formulation of relativistic dissipative hydrodynamics which preserves the causality. We found that the relaxation time plays an important role and also affects the angle of the Mach cone.