1992 (IPP)
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Item Toward a path integral for pure spin connection formulation of gravity(2014-11-26) Kshirsagar, A.K.A proposal for the path-integral of pure-spin-connection formulation of gravity is described, based on the two-form formulation of Capovilla et. al. It is shown that the resulting effective-action for the spin-connection, up on functional integration of the two-form field Σ and the auxiliary matrix field ψ is non-polynomial, even for the case of vanishing cosmological constant and absence of any matter couplings. Further, a diagrammatic evaluation is proposed for the contribution of the matrix-field to the pure spin connection action.Item Generation of seed perturbations from quantum cosmology(2014-11-26) Souradeep, TarunThe origin of seed perturbations in the Universe is studied within the framework of a specific mini super space model. It is shown that the ‘creation’ of the Universe as a result of a quantum transition from a flat empty space time would lead to a flat FLRW (Friedmann Lemaitre Robertson- Walker) Universe with weak inhomogeneous perturbations at large wavelengths. The power spectrum of these perturbations is found to be scale invariant at horizon crossing (i.e., the Harrison- Zeldovich spectrum). It is also recognised that the seed perturbations generated in our model would be generically of the isocurvature kind.Item Gravity without metric(2014-11-25) Kshirsagar, A.K.A recent development in gravity theories is described. It is shown that a complete description of gravity is possible without explicit reference to metric at all, instead in term of spin-connection variable. This represent a natural covariantisation of Ashtekars new variables approach to gravity. The gravity without metric action is particularly suitable for a Yang-Mills type quantization. I describe this theory in some detail, in a non-technical manner.Item On gravitational charge of stationary spacetimes(2014-11-23) Dadhich, NareshWe point out that ours is a definition of gravitational charge and not of quasilocal mass [1] we have defined gravitational charge as the flux of effective gravitational acceleration across a closed 2- surface. It turns out that tidal force can change its sense from convergence to divergence outside the horizon for suitable range of values of rotation and electric charge parameters of the black hole.