Shear viscosities from the Chapman-Enskog and the relaxation time approaches

Wiranata, Anton; Prakash, Madappa

doi:10.1103/physrevc.85.054908

Cited by 68 publications

(62 citation statements)

References 39 publications

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“…The Green-Kubo formalism relates linear transport coefficients to near-equilibrium correlations of dissipative fluxes and treats them as perturbations to local thermal equilibrium. A comparative study of the three different methods has been carried out by Wiranata and Prakash [30], In the varied cases considered there, the Green-Kubo technique is found to be more reliable. In Ref.…”

Section: Introductionmentioning

confidence: 97%

Shear viscosity and phase diagram from Polyakov–Nambu–Jona-Lasinio model

et al. 2015

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We present a detailed study of the variation of shear viscosity rj, with temperature and baryon chemical potential within the framework of the Polyakov-Nambu-Jona-Lasinio model, rj is found to depend strongly on the spectral width of the quasiparticles present in the model. The variation of rj across the phase diagram has distinctive features for different kinds of transitions. These variations have been used to study the possible location of the critical end point and are cross-checked with similar studies of variations of specific heat. Finally, using a parametrization of the freeze-out surface in heavy-ion collision experiments, the variation of the shear viscosity to entropy density ratio has also been discussed as a function of the centerof-mass energy of collisions.

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Section: Introductionmentioning

confidence: 97%

Shear viscosity and phase diagram from Polyakov–Nambu–Jona-Lasinio model

et al. 2015

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“…Being the QGP created at HICs a system far from equilibrium, the study of its transport coefficients is attracting a great interest. The η has been studied extensively [20][21][22][23][24][25][26][27][28][29]. Only very recently the electric conductivity, that represents the response of a system to the applied electric field, has captured a significative importance in the field of strongly interacting matter for many motivations.…”

Section: Introductionmentioning

confidence: 99%

Electric conductivity from the solution of the relativistic Boltzmann equation

2014

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We present numerical results of electric conductivity σ el of a fluid obtained solving the Relativistic Transport Boltzmann equation in a box with periodic boundary conditions. We compute σ el using two methods: the definition itself, i.e. applying an external electric field, and the evaluation of the Green-Kubo relation based on the time evolution of the current-current correlator. We find a very good agreement between the two methods.We also compare numerical results with analytic formulas in Relaxation Time Approximation (RTA) where the relaxation time for σ el is determined by the transport cross section σtr, i.e. the differential cross section weighted with the collisional momentum transfer. We investigate the electric conductivity dependence on the microscopic details of the 2-body scatterings: isotropic and anisotropic cross-section, and massless and massive particles. We find that the RTA underestimates considerably σ el ; for example at screening masses mD ∼ T such underestimation can be as large as a factor of 2. Furthermore, we study a more realistic case for a quark-gluon system (QGP) considering both a quasi-particle model, tuned to lQCD thermodynamics, as well as the case of a pQCD gas with running coupling. Also for these cases more directly related to the description of the QGP system, we find that RTA significantly underestimate the σ el by about a 60 − 80%.

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“…Further, lattice simulations at finite chemical potentials have been challenging and are limited only to small baryon chemical potential. This has lead to attempts to estimate shear viscosity in various effective models [6][7][8][9][10][11][12] involving different approximation schemes. These include relaxation time approximations to the Boltzmann equation [13][14][15][16][17][18], Kubo formalism of evaluating equilibrium correlation functions [19][20][21][22][23][24][25], transport simulation of Boltzmann equation [6,[26][27][28], the perturbative QCD methods [29][30][31][32][33][34][35][36], as well as lattice methods [37,38].…”

Section: Introductionmentioning

confidence: 99%

Shear viscosity η to electrical conductivity σel ratio for an anisotropic QGP

et al. 2017

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We study the transport properties of strongly interacting matter in the context of ultrarelativistic heavy ion collision experiments. We calculate the transport coefficients viz. shear viscosity (η) and electrical conductivity (σ el ) of the quark gluon plasma phase in the presence of momentum anisotropy arising from different expansion rates of the medium in longitudinal and transverse direction. We solve the relativistic Boltzmann kinetic equation in relaxation time approximation to calculate the shear viscosity and electrical conductivity. The calculation are performed within the quasiparticle model to estimate these transport coefficients and discuss the connection between them. We also compare the electrical conductivity results calculated from the quasiparticle model with the ideal case. We compare our results with the corresponding results obtained in different lattice as well as model calculations.

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Shear viscosities from the Chapman-Enskog and the relaxation time approaches

Cited by 68 publications

References 39 publications

Shear viscosity and phase diagram from Polyakov–Nambu–Jona-Lasinio model

Shear viscosity and phase diagram from Polyakov–Nambu–Jona-Lasinio model

Electric conductivity from the solution of the relativistic Boltzmann equation

Shear viscosity η to electrical conductivity σel ratio for an anisotropic QGP

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