Carrollian Origins of Bjorken Flow

TL;DR

This paper demonstrates that Bjorken flow, a model of relativistic fluids, can be fully described by Carrollian fluids, revealing that Carrollian hydrodynamics is a natural framework for near-light-speed fluid motion.

Contribution

It establishes a direct connection between Bjorken flow and Carrollian fluids, showing that Carrollian symmetries naturally emerge on null surfaces for high-speed relativistic flows.

Findings

Bjorken flow is captured by Carrollian hydrodynamics.

Carrollian symmetries arise on null surfaces for near-light-speed fluids.

Carrollian hydrodynamics is a general framework for relativistic fluids.

Abstract

Bjorken flow is among the simplest models of fluids moving near the speed of light ($c$) while Carroll symmetry arises as a contraction of Poincar\'{e} group when $c \to 0$. We show that Bjorken flow and its phenomenological approximations are completely captured by Carrollian fluids. Carrollian symmetries arise on generic null surfaces and a fluid moving at $c$ is restricted to such a surface, thereby naturally inheriting the symmetries. Carrollian hydrodynamics is thus not exotic, but rather ubiquitous, and provides a concrete framework for fluids moving at or near the speed of light.