1999 (IPP)

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    Search for continuous gravitational wave signals from sources in binary system
    (2015-03-01) Dhurandhar, S.V.; Vecchio, Albert
    We analyze the computational costs of searches for continuous monochromatic gravitational waves emitted by rotating neutron stars orbiting a companion object. As a function of the relevant orbital parameters, we address the computational load involved in targeted searches, where the position of the source is known; the results are applied to known binary radio pulsars and Sco-Xl.
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    Magnetic fields of neutron stars
    (2015-03-01) Konar, Sushan; Bhattacharya, Dipankar
    The evolution of the magnetic field is investigated for isolated as well as binary neutron stars. The overall nature of the field evolution is seen to be similar for an initial crustal field and an expelled flux. The major uncertainties of the present models of field evolution and the directions in which further investigation are required are also discussed in detail.
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    Correlations among global photometric properties of disk galaxies
    (2015-03-01) Khosroshahi, Habib G.; Wadadekar, Yogesh; Kembhavi, A.K.
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    Aspects of gravitational clustering
    (2015-03-01) Padmanabhan, T.
    Several issues related to the gravitational clustering of collisionless dark matter in an expanding universe is discussed. The discussion is pedagogical but the emphasis is on semianalytic methods and open questions-rather than on well established results.
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    A novel approach to particle production in an uniform electric field
    (2015-03-01) Srinivasan, K.; Padmanabhan, T.
    We outline a different method of describing scalar field particle production: in a uniform electric field. In the standard approach, the (analytically continued) harmonic oscillator paradigm is important in describing particle production. In the gauges normally considered, in which the four vector potential depends only on the time or space coordinate, the system reduces to a non-relativistic effective Schri:idinger equation with an inverted oscillator potential. The Bogolubov coefficients are determined by tunnelling in this potential. In the Schwinger proper time method of determining the effective Lagrangian, the analytically continued propagator for the usual oscillator system is regarded as the correct propagator for the inverted oscillator system and is used to obtain the gauge invariant result. However, there is another gauge in which the particle production process has striking similarities with the one used to describe Hawking radiation in black holes. This gauge we use to describe the electric field in is the lightcone gauge, so named because the mode functions for a scalar field are found to be singular on the lightcone. We use these modes in evaluating the effective Lagrangian using the proper time technique. The key feature of this analysis is that these modes can be explicitly "normalized" by using the criterion that they reduce to the usual flat space modes in the limit of the electric field tending to zero. This normalization procedure allows one to determine the Schwinger proper time kernel without using the analytical continuation of the harmonic oscillator kernel that is resorted to in the standard analysis. We find that the proper time kernel is not the same as the analytically continued oscillator kernel though the effective Lagrangian is the standard result as it should be. We also consider an example of a confined electric field system using the lightcone gauge modes that has several features of interest. In particular, our analysis indicates that the Bogolubov coefficients, in taking the limit to the uniform electric field case, are multiplied by energy dependent boundary factors that have not been taken into account before.
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    Reconstructing the cosmic equation of state from supernova distances
    (2015-03-01) Saini, Tarun Deep; Raychaudhuri, Somak; Sahni, Varun; Strarobinsky, A.A.
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    Domain walls in kaluza-klein spacetime
    (2015-03-01) Patel, L.K.; Dadhich, Naresh; Tikekar, R.
    Three families of exact solutions of Einstein field equations are found. Each family contains three parameters. Two of these families represent thick domain walls in a five dimensional Kaluza-Klein spacetime.The dynamical behaviour of our models is briefly discussed. The spacetime in all the cases is found to be reflection symmetric with respect to the wall.