1992 (IPP)

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    Quantum effects near a point mass in 2+1 dimensional gravity
    (2014-11-26) Souradeep, Tarun; Sahni, Varun
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    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.
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    Generation of seed perturbations from quantum cosmology
    (2014-11-26) Souradeep, Tarun
    The 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.
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    Flat spacetime cosmology: A unified framework for extragalactic redshifts
    (2014-11-26) Narlikar, J. V.; Arp, H. C.
    It is known that the standard Friedmann cosmology with k = 0 can be described equivalently in a conformal frame in which the spacetime is Minkowskian but all particle masses uniformly scale with epoch. In a Machian theory of gravity this spacetime dependence of mass is understood in terms of inertial interactions. This picture is shown to be more versatile than standard cosmology because it allows one to interpret objects of anomalously high redshift to be 'young' objects whose particle masses are lagging behind the universal mass function. We discuss here a variety of extragalactic phenomena within the framework of this model and show that these can be understood without recourse to adjustable parameters such as evolution, cosmological constant, etc.
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    The search for gravitational waves
    (2014-11-26) Dhurandhar, S.V.
    The direct detection of gravitational waves is one of the most challenging problems in experimental physics today. Sustained efforts have led to impressive advances on both theoretical and experimental fronts. This article first deals with the theoretical aspects of gravitational waves and then continues on to describe the detectors in vogue, the present status and various gravitational waves sources.
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    Cylindrically symmetric viscous universes
    (2014-11-26) Patel, L.K.; Dadhich, Naresh
    We have considered here cylindrically symmetric cosmological models with viscous fluid having the Kasnerian time evolution. It turns out that the ‘‘no‐matter’’ limit of our geodetic viscous universes, which can as well be looked upon as string dust universes, is the non-flat empty Kasner spacetime. We thus propose that the universe may be born with the Kasner geometry at t = 0 with matter in the form of viscous fluid, then it may follow the path: geodetic to non-geodetic and finally to the radiation phase when viscosity is fully worn out. We have solutions to describe each phase separately.
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    Cylindrical universes with heat and null radiation flow
    (2014-11-25) Patel, L.K.; Dadhich, Naresh
    In paper-I(Patel and Dadhich ,1992) we have discussed cylindrically symmetric viscous fluid models with the Kasnerian time evolution. In this paper we incorporate heat flow and null radiation flow with the perfect fluid. Here again, in the case of heat flow the Kasner spacetime is the matter-free limit of the model. We establish a general result that a static perfect fluid distribution will on Kasnerization (introduce t4/3, t4/3, and t−2/3 in the coefficients of dr2, dΦ2, and dz2) yield a time-dependent distribution with the same equation of state and with or without heat flow.
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    Choice of filters for the detection of gravitational waves from coalescing binaries II: detection in coloured noise
    (2014-11-25) Dhurandhar, S.V.; Sathyaprakash, B.S.
    We discuss the problem of detecting gravitational waves signals embedded in coloured noise from coalescing binary systems. The signal is assumed to be Newtonian and matched filtering techniques are employed to filter out the signal. The problem is discussed at first for a general power spectral density of the noise and then specific numerical results are obtained for the standard recycling case. Since the signal parameters are unknown, a bank of filters is needed to carry out the signal detection. The number of filters in a bank , the spacing between filter etc. is obainted for different values of minimum strength of the signal relative to the threshold. We also present an approximate analytical formula which relates the spacing between filter to the minimum strength. Finally we discuss the problem of detection probabilities given a data train.
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    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.