Research Papers (JVN)

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Author: search.filters.author.Narlikar, J. V.Subject: search.filters.subject.Astrophysics

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Now showing 1 - 9 of 9
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    Indian achievement in astronomy, astrophysics, relativity and cosmology
    (PHISPC, 2009-03-13) Narlikar, J. V.
    The chapter begins with describing the pioneering work of Meghnad Saha on stellar atmospheres, followed by the work in general relativity and cosmology in two distinct schools: N. R. Sen in Calcutta and V. V. Narlikar in Banaras. P. C. Vaidya's work (Banaras) on radiating stars is very much used today, as is B. Dart's (Calcutta) work on gravitational collapse. The Raychaudhuri equation in relativistic cosmology set the trend for future work on space-time singularities in general relativity. India has been one of the major places where alternatives (J. V. Narlikar) to the big bang cosmology have flourished. The Madras Observatory made its mark in optical observations, but post-independence India saw new facilities being created at Nainital, Kodaikanal, Kavalur, Udaipur, Gurushikhar, Han Le and Giravali. Space astronomies took off with balloons, rockets and satellites. The chapter ends with a brief critique of what have been the strengths of Indian contributions to astronomy and astrophysics, and their possible weaknesses.
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    Anomalous redshifts of quasi-stellar objects
    (American Astronomical Society, 1980-09-01) Narlikar, J. V.; Das, P. K.
    This paper is based on the assumption that the observational evidence to date does point to the possibility that high-redshift quasars are physically associated with low-redshift galaxies. It is first argued that the excess (or anomalous) redshifts of the quasars in such associations are unlikely to be either of Doppler or of gravitational origin. A new source for this excess redshift was suggested by Narlikar on the basis of the Hoyle-Narlikar theory of gravitation which is based on Mach's principle. This idea is applied to the hypothesis that quasars may have been ejected from galactic nuclei. The dynamics of such an ejection and its observable consequences are discussed. In particular, it is shown that quasar alignments and redshift bunching which have been observed recently can be understood within the framework of this theory. Further tests of this hypothesis are discussed.
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    Gravitational screens and superluminal separation in quasars
    (American Astronomical Society, 1980-01-15) Chitre, S. M.; Narlikar, J. V.
    The differential bending of radio waves by a suitably placed 'gravitational screen' such as an intervening galaxy can lead to large magnification of the separation velocity of the components in the nuclear region of a quasar. It is suggested that the apparent superluminal separation of such components observed in some quasars by the VLBI techniques could be due to velocity magnifications of this type. The astrophysical feasibility of this explanation is critically examined, and an optical search for objects of large mass-to-light ratio en route to quasars showing superluminal separation is advocated.
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    Role of white holes in astrophysics
    (Macmillan, 1978-01-20) Narlikar, J. V.
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    Role of general relativity in astrophysics
    ((B.H.U., 1976-01-11) Narlikar, J. V.
    It gives me great pleasure to attend this Seminar dedicated to the^Diamond Jubilee celebrations of my alma mater. I have happy recollections of attending lectures in this very lecture theatre as a student in 1955-57. While talking about general relativity may 1 also point out that this subject is about as old as this University. The first paper on this subject by Einstein' " appeared in Novem- ber 1915.
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    White holes and high energy astrophysics
    (Kluwer Academic Publishers, 1975-01-01) Narlikar, J. V.; Apparao, K. M. V.
    The role of exploding objects in high-energy astrophysics is discussed. Quantitative results are obtained for the simple case of the canonical white hole which explodes from a singularity and consists of pressure-free matter in the comoving frame of reference. General relativity is used for calculating the dynamical results. Applications to X-ray background, transient X-ray sources, gamma-ray bursts, and high energy cosmic rays are considered. White holes of more general types are discussed in a qualitative manner.
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    Gravitational searchlight and its astrophysical applications
    (Nature Publishing Group, 1974-12-06) Chitre, S. M.; Narlikar, J. V.; Kapoor, R. C.
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    Minibangs in cosmology and astrophysics
    (Springer, 1974-01-12) Narlikar, J. V.
    The ideas originally proposed to discuss continuous creation of matter are reconsidered in the context of the big bang cosmological models. It is shown that singularity-free big bang models are possible under the modified field equations of general relativity. However, the case is made out that matter creation takes place in several mini-bangs at different epochs rather than in one big bang. The implications of this idea for high energy astrophysics and for gravitational radiation are discussed.
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    High energy phenomena in astrophysics
    (D.A.E., 1972-12-12) Narlikar, J. V.