# Large fluctuations in non-ideal coarse-grained systems

## TL;DR

This paper investigates fluctuations in non-ideal systems using the MDLG approach, revealing that fluctuations do not diminish with coarse-graining as in ideal gases, impacting the accuracy of current hydrodynamics simulations.

## Contribution

It demonstrates the limitations of ideal gas assumptions in coarse-grained systems and highlights the need to modify existing fluctuating hydrodynamics models for non-ideal systems.

## Key findings

- Fluctuations persist in non-ideal systems upon coarse-graining.
- MDLG provides insights into the nature of fluctuations in such systems.
- Current models may require augmentation for accurate non-ideal system simulation.

## Abstract

Using the recently introduced Molecular Dynamics Lattice Gas (MDLG) approach, we test fluctuations of coarse-grained quantities. We show that as soon as the system can no longer be considered an ideal gas fluctuations fail to diminish upon coarse-graining as is usually expected. These results suggest that current approaches to simulating fluctuating hydrodynamics may have to be augmented to achieve quantitative results for systems with a non-ideal equation of state. The MDLG method gives a guidance to the exact nature of the fluctuation in such systems.