Hydrodynamics Off Equilibrium

 Having a thermalized system is the textbook requirement for the
applicability of hydrodynamics. However, there is mounting evidence
that hydrodynamics offers a good quantitative description even in
off-equilibrium situations. Recent applications of resurgence to
relativistic fluid dynamics in the context of conformal systems is
able to put the new, generalized theory of off-equilibrium fluid
dynamics on solid theoretical footing, without requiring near local
equilibrium or even isotropy. This offers a tempting explanation for
the ‘unreasonable success’ of hydrodynamics in describing experimental
data for p+p and p+A collisions.