Shear viscosity in a perturbative quark–gluon plasma

Fuini, John F.; Demir, Nasser; Srivastava, D. K.; Bass, Steffen A.

doi:10.1088/0954-3899/38/1/015004

Cited by 19 publications

(30 citation statements)

References 33 publications

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“…We notice that the exponential decay with time is not an assumption, but it comes directly from the calculation from the dynamical evolution in the simulation. We use this fact to fit the correlation function with the following expression, as done in several other works [39,41,43,30],…”

Section: Shear Viscosity From Green-kubo Relationmentioning

confidence: 99%

“…On the other a full HTL calculation as in Ref. [46] would require an energy dependent propagator with both longitudinal and transverse components, however our objective here it is not to have the best evaluation of η/s, but to discuss the comparison between CE, RTA and the numerical Green-Kubo method for a quite realistic case and also under the same condition of previous work based on the Green-Kubo method [41]. The total cross section in this scheme is energy and temperature dependent:…”

Section: Viscosity Of a Gluon Plasmamentioning

confidence: 99%

“…The Green-Kubo method in the contest of a relativistic plasma have been discussed also by other groups for the hadronic sector [43,30] and also in the QCD sector employing the pQCD matrix elements for 2 → 2 collisions [41] and more recently also for 2 → 2 and 2 → 3 collisions [39]. An alternative method based directly on the stationary velocity gradients has been developed showing an excellent agreement with the Green-Kubo method [40].…”

Section: Introductionmentioning

confidence: 98%

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Shear viscosity of a strongly interacting system: Green-Kubo correlator versus Chapman-Enskog and relaxation-time approximations

et al. 2012

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The shear viscosity η has been calculated by using the Green-Kubo relation in the framework of a partonic transport approach solved at cascade level. We compare the numerical results for η obtained from the Green-Kubo correlator with the analytical formulas in both the Relaxation Time Approximation (RTA) and the Chapman-Enskog approximation (CE). We investigate and emphasize the differences between the isotropic and anisotropic cross sections and between the massless and massive particles. We show that in the range of temperature explored in a Heavy Ion collision and for pQCD-like cross section the RTA significantly underestimates the viscosity by about a factor of 2-3, while a good agreement is found between the CE approximation and GreeKubo relation already at first order of approximation. The agreement with the CE approximation supplies an analytical formula that allows to develop kinetic transport theory at fixed shear viscosity to entropy density ratio, η/s. This open the possibility to explore dissipative non-equilibrium evolution of the distribution functions vs T-dependent η/s and particle momenta in the dynamics of the Quark-Gluon Plasma created in ultra-relativistic heavy-ion collisions.

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Section: Shear Viscosity From Green-kubo Relationmentioning

confidence: 99%

Section: Viscosity Of a Gluon Plasmamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

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Shear viscosity of a strongly interacting system: Green-Kubo correlator versus Chapman-Enskog and relaxation-time approximations

et al. 2012

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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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“…In Ref. [17] the shear viscosity of a QGP was calculated employing two-particle scatterings, i.e. without taking into account the radiative processes.…”

Section: Introductionmentioning

confidence: 99%

Shear viscosity of an ultrarelativistic Boltzmann gas with isotropic inelastic scattering processes

Lauciello

Wesp

et al. 2014

Nuclear Physics A

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We derive an analytic expression for the shear viscosity of an ultra-relativistic gas in presence of both elastic 2 → 2 and inelastic 2 ↔ 3 processes with isotropic differential cross sections.The derivation is based on the entropy principle and Grad's approximation for the off-equilibrium distribution function. The obtained formula relates the shear viscosity coefficient η to the total cross sections σ 22 and σ 23 of the elastic resp. inelastic processes. The values of shear viscosity extracted using the Green-Kubo formula from kinetic transport calculations are shown to be in excellent agreement with the analytic results which demonstrates the validity of the derived formula.

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Shear viscosity in a perturbative quark–gluon plasma

Cited by 19 publications

References 33 publications

Shear viscosity of a strongly interacting system: Green-Kubo correlator versus Chapman-Enskog and relaxation-time approximations

Shear viscosity of a strongly interacting system: Green-Kubo correlator versus Chapman-Enskog and relaxation-time approximations

Electric conductivity from the solution of the relativistic Boltzmann equation

Shear viscosity of an ultrarelativistic Boltzmann gas with isotropic inelastic scattering processes

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