Research Publications

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Author: search.filters.author.Joshi, P. S.Subject: search.filters.subject.Spacetime

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    Conformal quantization and space-time singularity
    (World Scientific Publishing group, 1986-06-06) Joshi, P. S.; Narlikar, J. V.
    This work generalizes earlier results of conformal quantization that within the full range of space-times conformal to any singular space-time satisfying Einstein's field equations for minimally coupled matter, the singular solutions form a set of zero-probability measure. A wider definition of space-time singularity that includes the curvature singularity assumed in the earlier work (op. cit.) is adapted and it is shown that the previous conclusion stands even when the present state of the universe is defined by wave functionals that are not necessarily wave packets. Within the present framework of quantum gravity therefore it seems extremely unlikely that the universe had a singular origin.
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    Bounds on vacuum energy density in a general cosmological scenario
    (Elsevier Science Publishers, 1987-02-09) Joshi, P. S.; Padmanabhan, T.; Chitre, S. M.
    General limits on the cosmological constant (or equivalently the vacuum energy density) are derived for an inflationary universe. This is accomplished under the general assumption of global hyperbolicity and without the use of any special properties like spherical symmetry or homogeneity ofthe underlying spacetime. Aclear upper limit of 1/3 is obtained for the vacuum energy density parameterQ~,while the lower limit is found to depend on the age of the oldest object in the universe.