On the implications of perfect fluids in metric-affine spacetime

The condition for a perfect fluid in the metric-affine extension of the Rie mannian spacetime of general relativity is determined. The condition for a pure perfect fluid without any additional interactions imposes a very stron g restriction bn the continuity relation for the fluid. The effect of this restriction is to remove both the torsion and the Weyl vectors from the fie ld equations. This shows that for matter described entirely by a perfect fl uid, the continuity relation for the fluid must take its general relativist ic form. This results opens up an entirely new arena in gravitational physi cs for the systematic investigation of various fluids with additional matte r fields in metric-affine geometry. It is also shown for the case of symmet ry breaking terms that break projective invariance of the Riemann scalar La grangian that the restrictive condition on the perfect fluid can be relaxed ; however this method of extending fluids to the full metric-affine geometr y, as is already known, will introduce unknown coupling constants into the theory.