Gradient expansion for anisotropic hydrodynamics

Understand

We compute the gradient expansion for anisotropic hydrodynamics.

• The results are compared with the corresponding expansion of the underlying kinetic-theory model with the collision term treated in the relaxation time approximation.
• We find that a recent formulation of anisotropic hydrodynamics based on an anisotropic matching principle yields the first three terms of the gradient expansion in agreement with those obtained for the kinetic theory.
• This gives further support for this particular hydrodynamic model as a good approximation of the kinetic-theory approach.