More simply, the question is whether the dark matter has pressure, and thus can be described as a perfect fluid.

For a perfect fluid, another equation of state relating density and pressure must be added.

Gives many examples of exact perfect fluid and dust solutions.

In particular, this enables us to quantize perfect fluid models.

Substitute the perfect fluid stress tensor for the matter sources.

Non-interacting dust ( a special case of perfect fluid ):

Perfect fluids are idealized models in which these possibilities are neglected.

A radiation fluid is a perfect fluid with :

However, they have found occasional application in the theory of static spherically symmetric perfect fluids.

Specifically, perfect fluids have no shear stresses, viscosity, or heat conduction.

(It might help to think of a perfect gas as a special case of a perfect fluid.)

Also, note that despite the names the strong energy condition does not imply the weak energy condition even in the context of perfect fluids.

Generating spherically symmetric static perfect fluid solutions (2000).

Perfect fluids admit a Lagrangian formulation, which allows the techniques used in field theory to be applied to fluids.

Perfect fluids are often used in general relativity to model idealized distributions of matter, such as in the interior of a star.

A perfect fluid has vanishing viscous shear and vanishing heat flux:

These are obviously scalar invariants, and they must vanish identically in the case of a perfect fluid solution:

This article describes one of several schemes recently found for obtaining all the static spherically symmetric perfect fluid solutions in general relativity.

The RHIC experiments also discovered that this matter is in fact strongly interacting and nearly a perfect fluid.

For such fluids, specific heats and are assumed to be constant and invariant with temperature (a thermally perfect fluid).

With stress-energy tensor for perfect fluid, we plug them into Einstein field equations and the resulting equations are described below.

Gödel dust contains contributions from a pressureless perfect fluid (dust) and from a positive vacuum energy.

In physics, a perfect fluid is a fluid that can be completely characterized by its rest frame mass density ρ and isotropic pressure p.

Sonic black holes are possible because phonons in perfect fluids exhibit the same properties of motion as fields, such as gravity, in space and time.

Pascal's Law, a law of hydrostatics is developed, stating that, in a perfect fluid, the pressure exerted on it anywhere is transmitted equally.