Research Papers (JVN)

Permanent URI for this collectionhttp://localhost:4000/handle/11007/400

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End date: 1979Subject: search.filters.subject.Cosmology

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Now showing 1 - 10 of 22
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    Tachyons and cosmology
    (S.N. Bose Institute, 1978-01-20) Narlikar, J. V.
    Cosmology and high energy astrophysics provide interesting settings for the study of faster than light particles, often called tachyons. Some examples of this are given and their possible implications are discussed.
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    Inertia and cosmology in Einstein's relativity
    (Johnson Reprint Corporation, 1979-01-02) Narlikar, J. V.
    Nature does not begin with elements, as we are obliged to begin with them. It is certainly fortunate for us, that we can, from time to time, turn aside our eyes from the overpowering unity ot" the All, and allow them to rest on individual details. Hut we should not omit, ultimately to complete and correct our views by a thorough consideration of the things which for the time being we left out of account.
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    Applications of statistical techniques to the angular size-flux density relation for extraglactic radio sources
    (Willy-Blackwell, 1977-01-14) Narlikar, J. V.; Chitre, S. M.
    The data on the angular sizes (theta) and flux densities (S) of extragalactic radio sources selected from two surveys are subjected to two independent statistical tests in order to determine whether the data warrant the conclusion that the universe is evolving. The nature of the observed scatter in the (theta, S) relation is examined, and a minimum chi-squared test is used to compare the observed (theta, S) plot with three theoretical models (one evolutionary and two nonevolutionary). A median test is then applied to compare the median angular sizes of two source samples in a narrow range of flux density. The results obtained indicate that due to the existing large scatter in the (theta, S) data, it is not possible to distinguish clearly between the evolutionary and the nonevolutionary models.
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    Quantum fluctuations in gravitational collapse and cosmology
    (Will-Blackwell, 1978-01-22) Narlikar, J. V.
    It is shown that the conformal degrees of freedom in the metric tensor can be quantized and that this procedure leads to fluctuations around the solutions of the classical Einstein field equations. These fluctuations become progressively more important as the classical solution approaches the space-time singularity. An explicit calculation is given of the quantum mechanical propagator which describes the conformal fluctuations in a collapsing homogeneous ball of dust. As the state of classical singularity is approached the quantum uncertainty diverges. Within the range of quantum uncertainty non-singular final states are possible. The solution can also be applied to the Friedmann models with the conclusion that the Universe need not have originated in a unique classical big bang. Non-singular models or models without particle horizons are permitted within the range of the quantum uncertainty.
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    Tachyons and cosmology
    (Royal Astronomical Society, 1976-01-15) Narlikar, J. V.; Sudarshan, E. C. G.
    The propagation of tachyons in an expanding universe is discussed. It is shown that a primordial tachyon in the big-bang universe cannot survive unless it had very large energy initially. In an indefinitely expanding universe, the tachyon trajectory turns back in time. This time barrier is found to exist even in the quantum-mechanical discussion of tachyons. This property is used to set limits on the mass of a tachyon. The possible astronomical checks on the hypothesis that neutrinos or photons may be tachyonic are also discussed.
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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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    Electrodynamics and cosmology
    (MIT, Press, 1974-01-11) Narlikar, J. V.
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    Thermodynamics and cosmology
    (John Wiley, 1974-01-11) Narlikar, J. V.
    Arguments are advanced to show that the time-asymmetry present in thermodynamics is likely to be strongly related to cosmology. It is also shown that not all models of the expanding universe provide a satisfactory link between thermodynamics and cosmology. Of the models usually discussed by the cosmologist only the steady state model has the required properties.
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    QSO redshifts and the steady state cosmology
    (Nature Publishing Group, 1975-12-25) Narlikar, J. V.; Das, P. K.
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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.