New theories of relativistic hydrodynamics in the LHC era

Understand

The success of relativistic hydrodynamics as an essential part of the phenomenological description of heavy-ion collisions at RHIC and the LHC has motivated a significant body of theoretical work concerning its fundamental aspects.

• Our review presents these developments from the perspective of the underlying microscopic physics, using the language of quantum field theory, relativistic kinetic theory, and holography.
• We discuss the gradient expansion, the phenomenon of hydrodynamization, as well as several models of hydrodynamic evolution equations, highlighting the interplay between collective long-lived and transient modes in relativistic matter.
• Our aim to provide a unified presentation of this vast subject -- which is naturally expressed in diverse mathematical languages -- has also led us to include several new results on the large-order behaviour of the hydrodynamic gradient~expansion.