Systematic errors in transport calculations of shear viscosity using the Green-Kubo formalism

Rose, Jean-Bernard; Torres-Rincón, Juan M.; Oliinychenko, Dmytro; Schäfer, A.; Petersen, Hannah

doi:10.1088/1742-6596/1024/1/012028

Cited by 6 publications

(10 citation statements)

References 13 publications

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“…A possible direction could be to explore denser systems beyond the exponential ansatz. Incidentally, the numerical time integration of the current-current correlation function is difficult to perform due to the huge uncertainties at large times [21].…”

Section: Discussionmentioning

confidence: 99%

“…The full phase space information of every particle in every time step is given by the SMASH output. As previously discussed in [21] there are different ways to extract the transport coefficient from the correlation function. In this work we choose to fit the average correlation function [see Eq.…”

Section: Methodsmentioning

confidence: 99%

“…Thus we follow the path started in our previous works, Refs. [21][22][23] focusing on shear viscosity, but now compute the electrical conductivity. Since SMASH constitutes a good description of various experimental data, like hadron properties and cross sections (see [13,24] for more details, and [25,26] for on-line examples of its performance), the value of the transport coefficients extracted in this work can be seen as a result restricted by experiment.…”

Section: Introductionmentioning

confidence: 99%

“…As observed in our previous study, Refs. [21,22], the lifetimes of the formed resonances might influence the relaxation of the fluctuations, affecting the transport coefficient at high temperatures. This is an important dynamical feature of the propagating resonances, which is absent in all previous studies based on semianalytical solutions of transport equations.…”

Section: Introductionmentioning

confidence: 99%

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Electrical conductivity and relaxation via colored noise in a hadronic gas

et al. 2019

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Motivated by the theory of relativistic hydrodynamic fluctuations we make use of the Green-Kubo formula to compute the electrical conductivity and the (second-order) relaxation time of the electric current of an interacting hadron gas. We use the recently developed transport code SMASH to numerically solve the coupled set of Boltzmann equations implementing realistic hadronic interactions. In particular, we explore the role of the resonance lifetimes in the determination of the electrical relaxation time. As opposed to a previous calculation of the shear viscosity we observe that the presence of resonances with lifetimes of the order of the mean-free time does not appreciably affect the relaxation of the electric current fluctuations. We compare our results to other approaches describing similar systems, and provide the value of the electrical conductivity and the relaxation time for a hadron gas at temperatures between T = 60 MeV and T = 150 MeV.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Electrical conductivity and relaxation via colored noise in a hadronic gas

et al. 2019

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“…So far it has been tested against exact solutions of Boltzmann equation [6], served as a basis to implement "thermal bubbles" model, where forced thermalization is performed wherever the energy density is high enough [7], used to compute the viscosity of a hadron gas [8] and to study dilepton production [9]. Most of the well-established hadronic resonances published by the Particle Data Group [10] with masses up to 2.5 GeV are implemented in SMASH.…”

Section: Model Descriptionmentioning

confidence: 99%

Bulk observables and dileptons at SIS energies with a new transport approach SMASH

Oliinychenko¹,

Steinberg²,

Staudenmaier³

et al. 2017

Proceedings of the European Physical Society Conference on High Energy Physics — PoS(EPS-HEP2017)

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Transport approaches are widely used to simulate heavy-ion collisions and allow to compute most experimental observables. In this contribution pion production, v 1 and v 2 of protons in Au+Au collisions at energies E lab = 0.4 − 2 A GeV and dilepton production in pp collisions at √ s = 3.5GeV are computed using a new SMASH transport approach. These results are compared to the experimental data obtained by the FOPI and HADES collaborations. Overall, a good description of the data is achieved. Pion multiplicities and N π − /N π + ratio at E lab = 0.4 − 0.8 A GeV are very sensitive not only to nuclear potentials, but also to Fermi motion and Pauli blocking effects. A good description of the proton v 1 and v 2 requires a nuclear potential corresponding to a hard equation of state.

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Inclusive and effective bulk viscosities in the hadron gas

Rose¹,

Torres-Rincón²,

Elfner³

2020

J. Phys. G: Nucl. Part. Phys.

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We estimate the temperature dependence of the bulk viscosity in a relativistic hadron gas. Employing the Green–Kubo formalism in the SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) transport approach, we study different hadronic systems in increasing order of complexity. We analyze the (in)validity of the single exponential relaxation ansatz for the bulk-channel correlation function and the strong influence of the resonances and their lifetimes. We discuss the difference between the inclusive bulk viscosity of an equilibrated, long-lived system, and the effective bulk viscosity of a short-lived mixture like the hadronic phase of relativistic heavy-ion collisions, where the processes whose inverse relaxation rate are larger than the fireball duration are excluded from the analysis. This clarifies the differences between previous approaches which computed the bulk viscosity including/excluding the very slow processes in the hadron gas. We compare our final results with previous hadron gas calculations and confirm a decreasing trend of the inclusive bulk viscosity over entropy density as temperature increases, whereas the effective bulk viscosity to entropy ratio, while being lower than the inclusive one, shows no strong dependence to temperature.

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Systematic errors in transport calculations of shear viscosity using the Green-Kubo formalism

Cited by 6 publications

References 13 publications

Electrical conductivity and relaxation via colored noise in a hadronic gas

Electrical conductivity and relaxation via colored noise in a hadronic gas

Bulk observables and dileptons at SIS energies with a new transport approach SMASH

Inclusive and effective bulk viscosities in the hadron gas

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