Research Papers (JVN)
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Item On the Hubble and the cosmological constant(Wiley-Blackwell, 1996-10-28) Hoyle, F.; Burbidge, G.; Narlikar, J. V.We review the observational determinations of the Hubble constant which have been made in recent years. We conclude that the most likely value of H_0 is 58 km s^-1 Mpc^-1 with uncertainties of +10 and -5. Thus the age of the standard big bang model is 11.2Gyr. The discrepancy between this value and the ages of the oldest observed stars, 13-16Gyr, appears to be real, necessitating some change in the standard model. A currently favoured procedure for coping with this widely-admitted difficulty for the theory which has been favoured by many cosmologists in recent years is a rebirth of the cosmological constant lambda. Even with this constant, the observations constrain the model very severely. There are theoretical considerations as well. The problem with this constant, as it has been seen over much of the past half-century, is that it is required to have a physical dimensionality of (length)^-2 and to have a magnitude of about 10^-56cm^-2. Theoreticians have not favoured introducing such a quantity ab initio into cosmology, but attempts to explain the genesis of lambda from particle physics have yielded results that are wide of what is required by immense factors (~10^50 to ~10^100). Using an approach from a scale-invariant theory of gravity, we show that lambda can be derived correct to a factor of ~2 within the modern Universe. This derivation does not appear to be applicable to earlier phases of the Universe, which give lambda~=H^2 rather than the relation lambda~=H^2_0 that a true cosmological constant would require.Item Quasi-steady state cosmology: analytical solutions of field equations and their relationship to observations(EDP Sciences, 1996-03-02) Sachs, R.; Narlikar, J. V.; Hoyle, F.We solve the cosmological equations obtained by Hoyle, Burbidge and Narlikar (1995a) from a Machian theory of gravity in the case where the universe satisfies the Weyl postulate and the cosmological principle. The equations in effect are the Einstein equations of general relativity together with a negative cosmological constant and a trace-free zero rest-mass scalar field. We find a wide range of solutions for spatial sections of zero, positive and negative curvature. The solution for the quasi-steady state cosmology used by Hoyle, Burbidge and Narlikar (1994 a,b) is shown to be an approximation to the simplest of the above solutions. We apply the simplest solution to work out the redshift-magnitude relation and the radio source count. We show that there are marginal differences from the results obtained by Hoyle et al (1994a), although the present exact solution provides a better rationale for the parameters of the model.