In physics, a perfect fluid is a fluid that can be completely characterized by its rest frame mass density and isotropic pressure p. Real fluids are "sticky" and contain (and conduct) heat. Perfect fluids are idealized models in which these possibilities are neglected. Specifically, perfect fluids have no shear stresses, viscosity, or heat conduction. Quark–gluon plasma is the closest known substance to a perfect fluid.
where U is the 4-velocity of the fluid and where is the metric tensor of Minkowski spacetime.
This takes on a particularly simple form in the rest frame
where is the energy density and is the pressure of the fluid.
Perfect fluids are used in general relativity to model idealized distributions of matter, such as the interior of a star or an isotropic universe. In the latter case, the equation of state of the perfect fluid may be used in Friedmann–Lemaître–Robertson–Walker equations to describe the evolution of the universe.
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- Mark D. Roberts, [A Fluid Generalization of Membranes http://www.arXiv.org/abs/hep-th/0406164 hep-th/0406164].