Collective Flow Global Collective Flow in Heavy Ion Reactions from the Beginnings to the Future

TL;DR

This paper reviews the evolution of fluid dynamical models in heavy ion reactions, emphasizing collective flow, instabilities, and the challenges of distinguishing turbulence from initial state fluctuations in Quark-gluon Plasma studies.

Contribution

It discusses early developments, key instabilities, their origins, and methods for detecting and separating collective flow effects from fluctuations in high energy heavy ion collisions.

Findings

Identification of collective flow instabilities and their origins.

Discussion on methods to detect and separate flow from fluctuations.

Highlighting the importance of turbulence and fluctuations in Quark-gluon Plasma.

Abstract

Fluid dynamical models preceded the first heavy ion accelerator experiments, and led to the main trend of this research since then. In recent years fluid dynamical processes became a dominant direction of research in high energy heavy ion reactions. The Quark-gluon Plasma formed in these reactions has low viscosity, which leads to significant fluctuations and turbulent instabilities. One has to study and separate these two effects, but this is not done yet in a systematic way. Here we present a few selected points of the early developments, the most interesting collective flow instabilities, their origins, their possible ways of detection and separation form random fluctuations arising from different origins, among these the most studied is the randomness of the initial configuration in the transverse plane.