• C V Vishveshwara

      Articles written in Pramana – Journal of Physics

    • Charged particle motion in an electromagnetic field on Kerr background geometry

      A R Prasanna C V Vishveshwara

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      In this paper we study the trajectories of charged particles in an electromagnetic field superimposed on the Kerr background. The electromagnetic fields considered are of two types: (i) a dipole magnetic field with an associated quadrupole electric field, (ii) a uniform magnetic field. The contribution of the background geometry to the electromagnetic field is taken through the solutions of Petterson and Wald respectively. The effective potential is studied in detail for ther-motion of the particles in the equatorial plane and the orbits are obtained. The most interesting aspect of the study is the illustration of the effect of inertial frame dragging due to the rotation of the central star. This appears through the existence of nongyrating bound orbits at and inside the ergo surface. The presence of the magnetic field seems to increase the range of stable orbits, as was found in a previous study involving the Schwarzschild background.

    • Neutrinos in gravitational collapse: Analysis of the flux profile

      S V Dhurandhar C V Vishveshwara

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      The flux profile of the neutrinos emitted from a collapsing spherical object, as seen by a remote observer is studied. The model of the collapsing star consists of the Friedmann dust interior matched onto the Schwarzschild exterior. It is assumed that the neutrino emission occurs from an interior shell in a very short time interval. It is found that the nature of the flux profile falls into four distinct categories depending on the progress of collapse. Interesting features such as bursts, discontinuities, decay, etc are observed when the collapse has sufficiently progressed.

    • Accretion onto a Kerr black hole in the presence of a dipole magnetic field

      B R Iyer C V Vishveshwara P J Wiita J J Goldstein

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      We analyze the accretion of charged matter onto a rotating black hole immersed in an aligned dipolar magnetic field. We specialize to motion in the equatorial plane and calculate the ‘Keplerian’ angular momentum distribution, the marginally stable and marginally bound orbits, and the efficiency of mass-to-energy conversion as functions of the angular momentum of the black hole and of the product of the dipole moment and the charge of the infalling matter. Although the detailed results are quite different from those previously obtained in the case of an uniform magnetic field, the astrophysically relevant results are very similar; when hydrodynamical accretion is considered, these effects of the magnetic field are always very small. But for test particles the efficiency can be significantly increased for limited ranges of the parameters.

    • The Vaidya solution in higher dimensions

      B R Iyer C V Vishveshwara

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      The Vaidya metric representing the gravitational field of a radiating star is generalized to spacetimes of dimensions greater than four.

    • Workshop I — Black holes and compact objects: Classical aspects

      B S Ramachandra C V Vishveshwara

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      This is a summary of the papers presented in session W1 on the papers submitted to the workshop I on the classical aspects of black holes and compact objects were classified into three categories: (i) theoretical aspects; (ii) astrophysical aspects; (iii) gravitational radiation. The three sessions were devoted each to one of the above categories. The chairmen of the workshop were J Bičák, Charles University, Prague (Czech Republic) and C V Vishveshwara, Indian Institute of Astrophysics, India.

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