From Full Stopping to Transparency in a Holographic Model of Heavy Ion Collisions

Abstract

We numerically simulate planar shock wave collisions in anti-de Sitter space as a model for heavy ion collisions of large nuclei. We uncover a cross-over between two different dynamical regimes as a function of the collision energy. At low energies the shocks first stop and then explode in a manner approximately described by hydrodynamics, in close similarity with the Landau model. At high energies the receding fragments move outwards at the speed of light, with a region of negative energy density and negative longitudinal pressure trailing behind them. The rapidity distribution of the energy density at late times around mid-rapidity is not approximately boost-invariant but Gaussian, albeit with a width that increases with the collision energy.

Effects of fluid velocity gradients on heavy quark energy loss

“…[30] and analyzed there and in refs. [31,32]. The matter produced in these collisions is initially far from equilibrium but then rapidly hydrodynamizes: its expansion and cooling is described well by viscous hydrodynamics after a time t hydro that is at most around (0.7 − 1)/T hydro , where T hydro is the effective temperature defined from the fourth root of the energy density at the hydrodynamization time t hydro .…”

“…[30] and analyzed there and in refs. [31,32]. The incident sheets of energy move at the speed of light in the z and −z directions and collide at z = 0 at time t = 0.…”

Holographic collisions in confining theories

“…By contrast, full non-linear simulations of collisions in AdS spacetime are in their infancy [3][4][5][6]. Validation of any such simulations requires benchmarking with perturbative results, either for the final ringdown stage or for intermediate stages of the process.…”

“…1 The study of these collision processes is challenging because one must solve Einstein's equations in a dynamical setting, which generically must be done numerically. Several such studies have now been performed in cases in which the gauge theory is a Conformal Field Theory (CFT) [3][4][5][6]. 2 The goal of this paper is to give a first step towards extending this program to gravitational duals of confining gauge theories.…”

Jet quenching and holographic thermalization with a chemical potential

“…The issue was studied by implementing various approaches in the literature. In [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] the collisions of gravitational shock waves are introduced to mimic the colliding nuclei in the relativistic collisions. In [24,25] time-dependent and boost-invariant metrics, associated with the plasma undergoing Bjorken expansion, were investigated and further generalized in [26] with a chemical potential.…”