Carrollian Origins of Bjorken Flow
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 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.
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