Holographic Gubser flow: A combined analytic and numerical study

TL;DR

This paper combines analytic and numerical methods to study Gubser flow in a holographic conformal field theory, revealing insights into its behavior and potential applications in heavy ion collision phenomenology.

Contribution

It provides the first numerical validation of analytic Gubser flow results and explores its behavior, including free-streaming and hydrodynamic regimes, in a holographic setting.

Findings

Large de Sitter time behavior is free-streaming in transverse directions.

Sub-leading behavior resembles a color glass condensate.

Pressure ratios converge to a hydrodynamic fixed point at large initial energies.

Abstract

Gubser flow is an evolution with cylindrical and boost symmetries, which can be best studied by mapping the future wedge of Minkowski space (R$^{3,1}$) to dS$_3$ $\times$ $\mathbb{R}$ in a conformal relativistic theory. Here, we sharpen our previous analytic results and validate them via the first numerical exploration of the Gubser flow in a holographic conformal field theory. Remarkably, the leading generic behavior at large de Sitter time is free-streaming in transverse directions and the sub-leading behavior is that of a color glass condensate. We also show that Gubser flow can be smoothly glued to the vacuum outside the future Minkowski wedge generically given that the energy density vanishes faster than any power when extrapolated to early proper time or to large distances from the central axis. We find that at intermediate times the ratio of both the transverse and longitudinal pressures to the energy density converge approximately to a fixed point which is hydrodynamic only for large initial energy densities. We argue that our results suggest that the Gubser flow is better applied to collective behavior in jets rather than the full medium in the phenomenology of heavy ion collisions and can reveal new clues to the mechanism of confinement.