Paths to equilibrium in non-conformal collisions

Attems, Maximilian; Casalderrey-Solana, Jorge; Matéos, David; Santos-Oliván, Daniel; Sopuerta, Carlos F.; Triana, Miquel; Zilhão, Miguel

doi:10.1007/jhep06(2017)154

Cited by 54 publications

(66 citation statements)

References 44 publications

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“…We note also that studies of non-equilibrium QGP dynamics using either the 2PI formalism or holography indicate that, in the highest temperatures probed during heavy-ion collisions, an equation of state may be established well before pressure isotropization occurs[22,24,50].…”

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confidence: 85%

Anisotropic nonequilibrium hydrodynamic attractor

2018

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We determine the dynamical attractors associated with anisotropic hydrodynamics (aHydro) and the DNMR equations for a 0+1d conformal system using kinetic theory in the relaxation time approximation. We compare our results to the non-equilibrium attractor obtained from exact solution of the 0+1d conformal Boltzmann equation, Navier-Stokes theory, and second-order Mueller-Israel-Stewart theory. We demonstrate that the aHydro attractor equation resums an infinite number of terms in the inverse Reynolds number. The resulting resummed aHydro attractor possesses a positive longitudinal to transverse pressure ratio and is virtually indistinguishable from the exact attractor. This suggests that kinetic theory involves not only a resummation in gradients (Knudsen number) but also a novel resummation in inverse Reynolds number. We also demonstrate that the DNMR result provides a better approximation to the exact kinetic theory attractor than Mueller-Israel-Stewart theory. Finally, we introduce a new method for obtaining approximate aHydro equations which relies solely on an expansion in inverse Reynolds number, carry out this expansion to third order, and compare these third-order results to the exact kinetic theory solution.

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confidence: 85%

Anisotropic nonequilibrium hydrodynamic attractor

2018

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“…In other words we must have L > 2π/k * . We follow the instability by numerically evolving the Einstein-plus-scalar equations as in [14,18]. From the dynamical metric we extract the boundary stress tensor.…”

Section: Initial Statementioning

confidence: 99%

Dynamics of phase separation from holography

Attems

Bea

Casalderrey-Solana

et al. 2020

J. High Energ. Phys.

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We use holography to develop a physical picture of the real-time evolution of the spinodal instability of a four-dimensional, strongly-coupled gauge theory with a firstorder, thermal phase transition. We numerically solve Einstein's equations to follow the evolution, in which we identify four generic stages: A first, linear stage in which the instability grows exponentially; a second, non-linear stage in which peaks and/or phase domains are formed; a third stage in which these structures merge; and a fourth stage in which the system finally relaxes to a static, phase-separated configuration. On the gravity side the latter is described by a static, stable, inhomogeneous horizon. We conjecture and provide evidence that all static, non-phase separated configurations in large enough boxes are dynamically unstable. We show that all four stages are well described by the constitutive relations of second-order hydrodynamics that include all second-order gradients that are purely spatial in the local rest frame. In contrast, a Müller-Israel-Stewart-type formulation of hydrodynamics fails to provide a good description for two reasons. First, it misses some large, purely-spatial gradient corrections. Second, several second-order transport coefficients in this formulation, including the relaxation times τ π and τ Π , diverge at the points where the speed of sound vanishes.

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“…Namely, the SO(3) quintuplet, triplet, and singlet channels are associated with the pressure anisotropy, the charge density, and the scalar condensate (dual to the bulk dilaton field), respectively. Under fairly general circumstances, the approach of each of these observables toward thermal equilibrium may provide many different characteristic relaxation time scales for the medium [81]. The approach of the pressure anisotropy toward zero gives us the so-called "isotropization time" of the system, while the last equilibration time of the medium is to be naturally identified as the actual "thermalization time" of the system.…”

Section: Quasinormal Modes and Equilibration Timesmentioning

confidence: 99%

Nonhydrodynamic quasinormal modes and equilibration of a baryon dense holographic QGP with a critical point

Rougemont¹,

Critelli²,

Noronha³

2018

Phys. Rev. D

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We compute the homogeneous limit of non-hydrodynamic quasinormal modes (QNM's) of a phenomenologically realistic Einstein-Maxwell-Dilaton (EMD) holographic model for the Quark-Gluon Plasma (QGP) that is able to: i) quantitatively describe state-of-the-art lattice results for the QCD equation of state and higher order baryon susceptibilities with 2+1 flavors and physical quark masses up to highest values of the baryon chemical potential currently reached in lattice simulations; ii) describe the nearly perfect fluidity of the strongly coupled QGP produced in ultrarelativistic heavy ion collisions; iii) give a very good description of the bulk viscosity extracted via some recent Bayesian analyzes of hydrodynamical descriptions of heavy ion experimental data. This EMD model has been recently used to predict the location of the QCD critical point in the QCD phase diagram, which was found to be within the reach of upcoming low energy heavy ion collisions. The lowest quasinormal modes of the SO(3) rotationally invariant quintuplet, triplet, and singlet channels evaluated in the present work provide upper bounds for characteristic equilibration times describing how fast the dense medium returns to thermal equilibrium after being subjected to small disturbances. We find that the equilibration times in the different channels come closer to each other at high temperatures, although being well separated at the critical point. Moreover, in most cases, these equilibration times decrease with increasing baryon chemical potential while keeping temperature fixed.

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Paths to equilibrium in non-conformal collisions

Cited by 54 publications

References 44 publications

Anisotropic nonequilibrium hydrodynamic attractor

Anisotropic nonequilibrium hydrodynamic attractor

Dynamics of phase separation from holography

Nonhydrodynamic quasinormal modes and equilibration of a baryon dense holographic QGP with a critical point

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