A Gravity Dual of RHIC Collisions

TL;DR

This work proposes a gravity dual for RHIC-like collisions within a variant of N=4 SYM, where the collision creates a holographic shower in AdS that collapses to a moving black hole, representing the expanding, cooling sQGP. The authors map the boundary processes—thermalization, cooling, and hadronization—to bulk dynamics including black-hole formation, its Hawking-Page transition, and brane cosmology of cooling. They derive that the fireball front cools as $T o 1/\tau$ and the core as $T\to 1/\sqrt{\tau}$, a rate faster than Bjorken cooling, with freeze-out linked to confinement via Hawking-Page. The work offers a qualitative, gravity-based picture for the entire heavy-ion collision evolution, shedding light on entropy production and non-ideal hydrodynamics in a strongly coupled gauge theory.

Abstract

In the context of the AdS/CFT correspondence we discuss the gravity dual of a heavy-ion-like collision in a variant of ${\cal N}=4$ SYM. We provide a gravity dual picture of the entire process using a model where the scattering process creates initially a holographic shower in bulk AdS. The subsequent gravitational fall leads to a moving black hole that is gravity dual to the expanding and cooling heavy-ion fireball. The front of the fireball cools at the rate of $1/τ$, while the core cools as $1/\sqrtτ$ from a cosmological-like argument. The cooling is faster than Bjorken cooling. The fireball freezes when the dual black hole background is replaced by a confining background through the Hawking-Page transition.

Figures (8)

• Figure 1: Wave functions of a few low energy glueball spectra.
• Figure 2: Probability distributions. Notice that $z=0$ is the boundary. For higher excitations it is more likely to be at UV region.
• Figure 3: Holographic correspondence of the expansion in 4d and the falling in 5d. From the boundary point of view, the front part '1' is freely streaming while the inner part '3' sees medium effects. From the bulk point of view: the lower part '1' falls freely while the upper part '3' sees the AdS black hole geometry. Birkhoff's theorem tells that whether the inner part is really black hole or not is not an issue. Thus the inner part '3' feels that it is in thermal equilibrium.
• Figure 4: At each interaction vertex of two scattering mesons a closed string must pop up. This is a unique feature of AdS space that does not take place easily in flat space.
• Figure 5: Multiple interaction vertices create a shower of massive closed strings in AdS space. Some of them are mini-black holes. The strings flake and fall towards the AdS center like a rain-fall to form a large black hole at bottom.