Towards hydrodynamics without an entropy current

Understand

We present a generating functional which describes the equilibrium thermodynamic response of a relativistic system to external sources.

• A variational principle gives rise to constraints on the response parameters of relativistic hydrodynamics without making use of an entropy current.
• Our method reproduces and extends results available in the literature.
• It also provides a technique for efficiently computing n-point zero-frequency hydrodynamic correlation functions without the need to solve the equations of hydrodynamics.