Akihiko Monnai

Effects of bulk viscosity at freezeout

We investigate particle spectra and elliptic flow coefficients in relativistic heavy-ion collisions by taking into account the distortion of phase space distributions by bulk viscosity at freezeout. We first calculate the distortion of phase space distributions in a multicomponent system with Grads 14-moment method. We find some subtle issues when macroscopic variables are matched with microscopic momentum distributions in a multicomponent system, and we develop a consistent procedure to uniquely determine the corrections to the phase space distributions. Next, we calculate particle spectra by using the Cooper-Frye formula to see the effect of the bulk viscosity. Despite the relative smallness of the bulk viscosity, we find that it is likely to have a visible effect on particle spectra and elliptic flow coefficients. This indicates the importance of taking into account bulk viscosity together with shear viscosity to constrain the transport coefficients with better accuracy from comparison with experimental data.

Thermal photonv2with slow quark chemical equilibration

Elliptic flow of direct photons in high-energy heavy ion collisions has been a topic of great interest as it is experimentally found larger than most hydrodynamic expectations. I discuss the implication of possible late formation of quark component in the hot QCD medium on the photon elliptic flow as quarks are the source of thermal photons in the deconfined phase. Hydrodynamic equations are numerically solved with the evolution equations for quark and gluon number densities. The numerical results suggest that thermal photon

Relativistic dissipative hydrodynamic equations at the second order for multi-component systems with multiple conserved currents

v_2

Dissipative hydrodynamic effects on baryon stopping

is visibly enhanced by the slow chemical equilibration of quarks and gluons, reducing the aforementioned problem.

Constraining the equation of state with identified particle spectra

Abstract We derive the second order hydrodynamic equations for the relativistic system of multi-components with multiple conserved currents by generalizing the Israel–Stewart theory and Grads moment method. We find that, in addition to the conventional moment equations, extra moment equations associated with conserved currents should be introduced to consistently match the number of equations with that of unknowns and to satisfy the Onsager reciprocal relations. Consistent expansion of the entropy current leads to constitutive equations which involve the terms not appearing in the original Israel–Stewart theory even in the single component limit. We also find several terms which exhibit thermal diffusion such as Soret and Dufour effects. We finally compare our results with those of other existing formalisms.

Longitudinal Viscous Hydrodynamic Evolution for the Shattered Colour Glass Condensate

The quark-gluon plasma is considered to behave as a relativistic viscous fluid in the high-energy heavy ion collisions. In this study, I develop and estimate a second order dissipative hydrodynamic model at finite baryon density with effects of baryon dissipation together with those of shear and bulk viscosities. It is found that the hydrodynamic evolution effectively reduces baryon stopping, suggesting that the collisions are less transparent at the initial stage. Also the net baryon distribution is found sensitive to baryon dissipation as well as to viscosities. The results indicate that the dissipative hydrodynamic modeling would be important for understanding unique properties of the hot medium even in the high-energy collisions.

Effects of Bulk Viscosity on pT-Spectra and Elliptic Flow Parameter

We show that in a central nucleus-nucleus collision, the variation of the mean transverse mass with the multiplicity is determined, up to a rescaling, by the variation of the energy over entropy ratio as a function of the entropy density, thus providing a direct link between experimental data and the equation of state. Each colliding energy thus probes the equation of state at an effective entropy density, whose approximate value is

Effective distributions of quasiparticles for thermal photons

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Dissipative hydrodynamic effects on the quark-gluon plasma at finite baryon density

fm

Off-equilibrium corrections to energy and conserved charge densities in the QGP fluid

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