The Relation Between Inhomogeneous Shear Anisotropy and Inflation in Relativistic Cosmology

The Friedmann-Robertson-Walker (FRW) models provide the best possible description of the present epoch of the observable universe. It is also true that the universe could have existed in its homogeneous and isotropic form for a very long time in its history. The isotropy assumption has been supported by measurements of the microwave background radiation. However, it has been observed by Khlopov and Polnarev [7] that in the early universe inhomogeneities might have evolved due to the creation of particles with thermal energy (kT) of the order equivalent to their rest mass energy (mc²) and lifetime exceeding the cosmological time scale. These initial inhomogeneities could have developed as seeds of the present day structures. Further, even at present there is evidence for inhomogeneities on the scales up to 10-100 Mps in the form of clusters and superclusters of galaxies. Also, the possibility of the existence of primordial gravitational waves, which are transverse in character, leads to anisotropy (see Krauss [8]).