# Relativistic fluid dynamics and its extensions as an effective field theory

## TL;DR

This paper presents a novel effective field theory approach to relativistic fluid dynamics, incorporating thermal fluctuations and extending the framework to complex systems like spin-polarized and gauge theories.

## Contribution

It introduces a unified EFT framework for hydrodynamics that includes thermal fluctuations and applies to systems with non-trivial microscopic structures.

## Key findings

- Thermal fluctuations can be systematically included in hydrodynamics.
- The approach extends hydrodynamics to spin polarization and gauge theories.
- The method provides a consistent way to handle microscopic complexities.

## Abstract

We examine hydrodynamics from the perspective of an effective field theory. The microscopic scale in this case is the thermalization scale, and the macroscopic scale is the gradient, with thermal fluctuations playing the role of $\hbar$. We argue that this method can be applied both, to consistently include thermal fluctuations in the theory, and to extend hydrodynamics to systems whose microscopic structure is non-trivial. For the latter, we discuss the case of spin polarization and gauge theories.