Causality of fluid dynamics for high-energy nuclear collisions

Understand

Dissipative relativistic fluid dynamics is not always causal and can favor superluminal signal propagation under certain circumstances.

• On the other hand, high-energy nuclear collisions have a microscopic description in terms of QCD and are expected to follow the causality principle of special relativity.
• We discuss under which conditions the fluid evolutions for a radial expansion are hyperbolic and how the properties of the solutions are encoded in the associated characteristic curves.
• The expansion dynamics is causal in relativistic sense if the characteristic velocities are smaller than the speed of light.