Hello All, I am stuck up in a concept, not on maths part. Gravitational force in General Theory is produced by mass, momentum, and stress density of a fluid. In metric theory of gravitation,a static symmetric perfect fluid solution has tensor fields which is similar to a static round ball of a fluid. The similarity is used for a perfect ideal condition in stars. Dark fluid is a concept that unites both dark matter and dark energy. My question is : (a) Is someway dark fluid related to the fluid solution of General Relativity? (b) Is the stress-energy tensor has been calculated particularly of a perfect fluid in order to study the details of stellar formations?