Tilted Bianchi VII_0 cosmologies -- the radiation bifurcation

Abstract

We derive the late-time behaviour of tilted Bianchi VII_0 cosmologies with an irrotational radiation fluid as source, and give the asymptotic form of the general solution as $t \to +\infty$, making comparisons with the dust-filled models. At first sight the radiation-filled models appear to approximate the flat FL model at late times, since the Hubble-normalized shear and the tilt tend to zero and the density parameter tends to one. The Hubble-normalized Weyl curvature diverges, however, indicating that physically significant anisotropy remains. We also discuss the influence of a cosmological constant on this phenomenon.