Fluid dynamics in higher order gravity (Q1340032)

We examine the kinematic and dynamic properties of fluid spacetimes in higher order gravity. In particular, we extend the general equations of Ehlers and Ellis governing relativistic fluid dynamics from general relativity to the higher order theory. We find exact results for the evolution of shear in Bianchi spacetimes with isotropic surfaces, thus generalising the general relativity results. Furthermore, we show that the Ehlers-Geren-Sachs theorem on cosmic background radiation also holds in the higher order theory.