ON SINGULARITY-FREE COSMOLOGICAL MODELS

In 1990 Senovilla(1) obtained an interesting 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, rho = 3 rho. The model was valid,for t --> - infinity to t --> infinity 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 (On). Subsequently a family of singularity-free models has been identified(2). In this communication we wish to point out that a simple and natural inhomogenization and anisotropization, 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.