Hydrodynamic attractors in heavy ion collisions: a review

Soloviev, Alexander

doi:10.48550/arxiv.2109.15081

Cited by 8 publications

(9 citation statements)

References 137 publications

(265 reference statements)

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“…Why exactly hydrodynamics works this well in describing a system which spends a large part of its evolution far from local equilibrium, and where gradients are not small [5], is currently under very active investigation [6,7]. Recent developments based on the bottom-up thermalization scenario [8,9] show that QCD effective kinetic theory (EKT) manifests hydrodynamic behaviour after a characteristic time τ R , provided that it is smaller than the system size R [10,11].…”

Section: Introductionmentioning

confidence: 99%

Mini-jet quenching in a concurrent jet+hydro evolution and the non-equilibrium quark-gluon plasma

Pablos,

Singh,

Jeon

et al. 2022

Preprint

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Mini-jets, created by perturbative hard QCD collisions at moderate energies, can represent a significant portion of the total multiplicity of a heavy-ion collision event. Since their transverse momenta are initially larger than the typical saturation scale describing the bulk of the equilibrating QGP, they ought to be described through the physics of parton energy loss. Indeed, their typical stopping distances are larger than the usual hydrodynamization time, so they do not in general hydrodynamize at the same pace than the bulk of the collision. Therefore, in general mini-jets cannot be described solely by a unique pre-equilibrium stage that bridges the initial, over-occupied glasma state, with the hydrodynamical evolution. In this work we make use of a new concurrent mini-jet+hydrodynamic framework in which the properties of the hydrodynamically evolving QGP are modified due to the injection of energy and momentum from the mini-jets. We study the system for different choices of the minimum transverse momentum associated to mini-jet production. In order to achieve a realistic description of charged particle multiplicity, the amount of entropy associated to the low-x initial state needs to be reduced. Moreover, the fact that the injected momentum from the randomly oriented mini-jets is not correlated with the spatial gradients of the system reduces overall flow, and the value of the QGP transport coefficients needs to be reduced accordingly in order to describe the measured flow coefficients in experiments. They are, in effect, an important new source of fluctuations, resulting in a spikier, notably modified hydrodynamical evolution when compared to the scenario in which the presence of mini-jets is ignored. We avow that their abundance makes it necessary to include their physics in holistic descriptions of heavy-ion collisions. We discuss the impact of the mini-jets on a number of observables, such as pT spectra and pT -differential flow vn for a wide range of centrality classes. In contrast to elliptic, triangular or quadrangular flow, we find that directed flow, v1, has the strongest potential to discriminate between different mini-jet production rates.

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Section: Introductionmentioning

confidence: 99%

Mini-jet quenching in a concurrent jet+hydro evolution and the non-equilibrium quark-gluon plasma

Pablos,

Singh,

Jeon

et al. 2022

Preprint

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“…and different theoretical [15][16][17][18][19][20][21][22][23] and phenomenological aspects of the emergence of hydrodynamic attractors [24][25][26][27] have been explored. See [28] for a recent review.…”

Section: Introductionmentioning

confidence: 99%

Exponential Approach to the Hydrodynamic Attractor in Yang-Mills Kinetic Theory

Du,

Heller,

Schlichting

et al. 2022

Preprint

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We use principal component analysis to study the hydrodynamic attractor in Yang-Mills kinetic theory undergoing the Bjorken expansion with Color Glass Condensate initial conditions. The late time hydrodynamic attractor is characterized by a single principal component determining the overall energy scale. How it is reached is governed by the disappearance of single subleading principal component characterizing deviations of the pressure anisotropy, the screening mass and the scattering rate. We find that for wide range of couplings the approach to the hydrodynamic attractor at late times is well described by an exponential. Its decay rate dependence on the coupling turns out to translate into a simple dependence on the shear viscosity to entropy density ratio.

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“…Regardless of its simplistic nature, the RTA turns out to be very useful and has been employed quite extensively to formulate relativistic dissipative hydrodynamics and derive the form of transport coefficients [5,[11][12][13][14][15][16]. Recently, it has also been employed to study the domain of applicability of hydrodynamics and study the hydrodynamization phenomena [17][18][19][20][21][22][23][24][25][26][27]. This simple model seems to capture the effective microscopic interaction for a wide range of theories.…”

Section: Introductionmentioning

confidence: 99%

Extended relaxation time approximation and relativistic dissipative hydrodynamics

Dash,

Bhadury,

Jaiswal

et al. 2021

Preprint

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Development of a new framework for derivation of order-by-order hydrodynamics from Boltzmann equation is necessary as the widely used Anderson-Witting formalism leads to violation of fundamental conservation laws when the relaxation-time depends on particle momenta, or in a hydrodynamic frame other than the Landau frame. We generalize an existing framework for consistent derivation of relativistic dissipative hydrodynamics from the Boltzmann equation with a momentum dependent relaxation-time by extending the Anderson-Witting relaxation-time approximation. We argue that the present framework is compatible with conservation laws and derive first-order hydrodynamic equations in landau frame. Further, we show that the transport coefficients, such as shear and bulk viscosity as well as charge and heat diffusion currents, have corrections due to the momentum dependence of relaxation-time compared to what one obtains from the Anderson-Witting approximation of the collision term. The ratio of these transport coefficients have been studied using a parametrized relaxation-time, and several novel and interesting scaling features are reported.

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Hydrodynamic attractors in heavy ion collisions: a review

Cited by 8 publications

References 137 publications

Mini-jet quenching in a concurrent jet+hydro evolution and the non-equilibrium quark-gluon plasma

Mini-jet quenching in a concurrent jet+hydro evolution and the non-equilibrium quark-gluon plasma

Exponential Approach to the Hydrodynamic Attractor in Yang-Mills Kinetic Theory

Extended relaxation time approximation and relativistic dissipative hydrodynamics

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