Forms of action for perfect fluid in General Relativity and mimetic gravity

Understand

We consider various forms of action allowing us to describe a perfect fluid in the framework of General Relativity.

• First we consider a potential motion without pressure.
• Starting from an action in terms of the current density vector built similarly to the action of a single particle, we build a series of equivalent actions through various changes of variables.
• The results are then generalized to the cases of motion with vorticity and the presence of pressure.