Research Papers (JVN)

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End date: 1999Subject: search.filters.subject.Universe

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Now showing 1 - 10 of 21
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    Did the universe have an origin?
    (Indian Journal of Physics, 1985-11-29) Narlikar, J. V.
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    Quantum cosmology and the early universe
    (Italian Physical Society, 1985-11-15) Narlikar, J. V.
    The classical Friedmann cosmology is known to suffer from three major conceptual problems :' (i) spacetime singularity; (ii) particle horizons and (iii) flatness. It is shown that these problems may be resolved during the quantum era of the early universe. Recent attempts in this direction based on the quantization of the conformal degrees of freedom are reviewed here.
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    Counter images in closed elliptical friedmann universes
    (American Astronomical Society, 1985-01-06) Narlikar, J. V.; Seshadri, T. R.
    It is shown that the different connectivity implied by the elliptical version of a closed Friedmann model allows two images of a distant astronomical object to be seen, provided the deceleration parameter q0 of the Friedmann model exceeds unity. Of the two images the direct image is along the shortest-route light track. If the redshift of the direct image exceeds (1.5q0 - 1)/(q0 - 1)sq then a second counterimage should be visible at the diametrically antipodal position. The direct image has a maximum possible redshift, and it is suggested that the apparent cutoff in the redshifts of QSOs may be due to this effect. Other observable consequences of this result are discussed in relation to galaxies and QSOs.
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    Quantum cosmology as a cure of three ailments of classical cosmology
    (Astronomical Society of India, 1983-08-12) Padmanabhan, T.; Narlikar, J. V.
    The standard big bang models of classical cosmology are known to possess three defects. The oldest known defect is spacetime singularity whose existence seems inevitable within the classical framework. The second defect is the existence of a particle horizon which severely limits communications across the distant parts of the universe whose observed homogeneity therefore becomes inexplicable. Recently a third defect has been highlighted, viz., the required fine tuning of the early universe close to the flat spatial model in order to account for the present range of its mean density. We show before that the injection of quantum ideas holds out hope of a cure for all the three ailments described above. Using a simple path integral formalism for quantum cosmology we present arguments which suggest that (i) it is extremely unlikely that the universe evolved to the present state from quantum states of singularity and particles horizon;(ii) of all the possible Robertson-Walker models that could evolve our of quantum fluctuations of the empty Minkowski universe the flat model is overwhelmingly probable.
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    Alternative cosmology: The QSSC
    (International Astronomical Union, 1999-03-24) Narlikar, J. V.
    This review begins with a brief survey of the observational constraints on the standard big bang cosmology, pointing out that the various limits leave a very narrow window in the parameter space of plausible models. There is thus a strong case for alternative cosmologies. The rest of the review concentrates on one alternative, the quasi steady state cosmology (QSSC) and summaries the recent work on this model. The includes the theoretical formulation and simple exact solution of the basic equations, their relationship to observations, the stability of solutions and the toy model for understanding the growth of structures in the universe.
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    Empirical approach to cosmology
    (Springer, 1981-01-23) Narlikar, J. V.; Burbidge, G.
    A two-component model of the universe is proposed, based on the observations of discrete extragalactic sources and the microwave background radiation. The large scale dynamics of the universe is determined by the radiation component and it leads to a characteristic size of the universe of approximately 600,000 Mpc and an age of approximately one trillion years. The second component, that of matter, occurs in discrete sources which group together in super-superclusters of characteristic size approximately 6000 Mpc and age 10 billion yr. It is suggested that the Galaxy belongs to one of these super-superclusters and that observations of discrete sources are confined to this unit. A reasonable agreement with the cosmological tests is obtained on the assumption that the geometry within a typical super-supercluster is Euclidean and that the redshifts of galaxies arise from a Doppler effect due to motions originating in a local explosion which gave birth to the super-supercluster. Further observational checks on this model are proposed.
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    Relativistic cosmology
    (Kluwer, Dordrecht, 1997-09-22) Narlikar, J. V.
    The subject of cosmology is an admixture of imaginative ideas, intuitive predictions and hard scientific facts. This has made cosmology a case of three distinct cultures; that of astronomers, who look at the universe and find hard data, relativists - who build models of universe that range from simple to esoteric ones, and the particle physicists who can test their the- ories of very high energy physics only in the cosmic laboratory that was there at the very onset of the universe. This culture can well be compared with the British culture, where one has three classes: the working class, the professionals and the aristrocrats. This course will try to give certain glimpses of cosmology in these three fields.
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    How universal is Hubble's law?
    (Indian Mathematical Society, 1995-05-18) Narlikar, J. V.
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    Cosmology and action at a distance electrodynamics
    (American Physical Society, 1995-04-24) Hoyle, F.; Narlikar, J. V.
    This article reviews the developments in the electrodynamics of direct interparticle action, em-phasizing the achievements in quantum as well as classical electrodynamics. It is shown that the application of the Wheeler-Feynman absorber theory of radiation places stringent requirements on the asymptotic future and past light cones of the universe. All Friedmann cosmologies fail to meet these requirements, but the steady-state and the quasi-steady-state models have the right kind of structure to make the theory work. Further, it is shown that the working theory is free from the problems of divergence that trouble the classical and quantum field theory. In particular, no renormalization is needed: The bare mass and bare charge of an electron are finite. A few ideas relating to the response of the universe to a local microscopic experiment are presented as well as on possible clues to the outstanding issues of foundations of quantum theory
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    How universal is Hubble's law?
    (World Scientific Publishing Company, 1995-03-24) Narlikar, J. V.