Coarse graining scale and effectiveness of hydrodynamic modeling

TL;DR

This paper examines how the choice of coarse-graining scale affects the effectiveness of hydrodynamic models in describing relativistic heavy ion collisions, highlighting limitations and indicators of initial condition inhomogeneity.

Contribution

It clarifies the role of coarse-graining scale in hydrodynamic modeling and proposes observable indicators for initial inhomogeneity without requiring full thermal equilibrium.

Findings

Certain observables can indicate initial inhomogeneity with less strict thermal equilibrium conditions.

The coarse-graining scale limits the space-time resolution of hydrodynamic models.

Hydrodynamic approach's applicability depends on the chosen coarse-graining scale.

Abstract

Some basic questions about the hydrodynamical approach to relativistic heavy ion collisions are discussed aiming to clarify how far we can go with such an approach to extract useful information on the properties and dynamics of the QCD matter created. We emphasize the importance of the coarse-graining scale required for the hydrodynamic modeling which determines the space-time resolution and the associated limitations of collective flow observables. We show that certain kinds of observables can indicate the degree of inhomogeneity of the initial condition under less stringent condition than the local thermal equilibrium subjected to the coarse-graining scale compatible to the scenario.