# A derivation of the entropy-based relativistic smoothed particle hydrodynamics by variational principle

## TL;DR

This paper develops a second order entropy-based relativistic smoothed particle hydrodynamics method using a variational principle, enhancing accuracy and consistency for modeling high-energy density fluids in heavy ion collisions.

## Contribution

It introduces a novel second order entropy-based relativistic SPH formulation derived via variational principles, ensuring improved translational invariance and particle consistency.

## Key findings

- Second order SPH guarantees better particle consistency.
- Variational principle preserves translational invariance.
- Potential applications in heavy ion physics.

## Abstract

In this work, a second order smoothed particle hydrodynamics is derived for the study of relativistic heavy ion collisions. The hydrodynamical equation of motion is formulated in terms of the variational principle. In order to describe the fluid of high energy density but of low baryon density, the entropy is taken as the base quantity for the interpolation. The smoothed particle hydrodynamics algorithm employed in this study is of the second order, which guarantees better particle consistency. Furthermore, it is shown that the variational principle preserves the translational invariance of the system, and therefore improves the accuracy of the method. A brief discussion on the potential implications of the model in heavy ion physics is also presented.