Hydrodynamic Approaches in Relativistic Heavy Ion Reactions

TL;DR

This review discusses the conceptual foundations, recent theoretical developments, and experimental implications of hydrodynamic models in relativistic heavy ion collisions, emphasizing the validity, derivations, and limitations of the approach.

Contribution

It provides a comprehensive overview of the physical basis, derivation methods, and recent advances in relativistic hydrodynamics applied to heavy ion collisions.

Findings

Analysis of the validity of hydrodynamic models

Discussion of derivation methods and limitations

Connection between hydrodynamics and microscopic models

Abstract

We review several facets of the hydrodynamic description of the relativistic heavy ion collisions, starting from the historical motivation to the present understandings of the observed collective aspects of experimental data, especially those of the most recent RHIC and LHC results. In this report, we particularly focus on the conceptual questions and the physical foundations of the validity of the hydrodynamic approach itself. We also discuss recent efforts to clarify some of the points in this direction, such as the various forms of derivations of relativistic hydrodynamics together with the limitations intrinsic to the traditional approaches, variational approaches, known analytic solutions for special cases, and several new theoretical developments. Throughout this review, we stress the role of course-graining procedure in the hydrodynamic description and discuss its relation to the physical observables through the analysis of a hydrodynamic mapping of a microscopic transport model. Several questions to be answered to clarify the physics of collective phenomena in the relativistic heavy ion collisions are pointed out.