On Singularity Free Cosmological Models

Abstract

In 1990 Senovilla$^1$ obtained an interestisng cosmological solution of Einstein's equations that was free of the big-bang singularity. It represented an inhomogeneous and anisotropic cylindrical model filled with disordered radiation, ${\bf ρ= 3p}$. The model was valid for ${\bf t \rightarrow - \infty }$ to ${\bf t \rightarrow \infty}$ having all physical and geometrical invariants finite and regular for the whole of spacetime. This was the first instance of a singularity free cosmological model satisfying all the energy and causality conditions and remaining true to general relativity (GR). Subsequently a family of singularity free models has been identified${\bf ^2}$. In this letter we wish to point out that a simple and natural inhomogenisation and anisotropisation, appropriate for cylindrical symmetry, of the Friedman-Robertson-Walker (FRW) model with negative curvature leads to the same singularity free family. It consists of the complete set of singularity free general solutions of Einstein's equations for perfect fluid when cylindrically symmetric metric potentials are assumed to be separable functions of radial and time coordinates.