Research Papers (JVN)
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Item Critique of supernova data analysis in cosmology(IOP Publishing, 2010-10-20) Vishwakarma, R. G.; Narlikar, J. V.Observational astronomy has shown significant growth over the last decade and has made important contributions to cosmology. A major paradigm shift in cos-mology was brought about by observations of Type Ia supernovae. The notion that the universe is accelerating has led to several theoretical challenges. Unfortunately, although high-quality supernovae data-sets are being produced, their statistical anal-ysis leaves much to be desired. Instead of using the data to directly test the model, several studies seem to concentrate on assuming the model to be correct and limiting themselves to estimating model parameters and internal errors. As shown here, the important purpose of testing a cosmological theory is thereby vitiated.Item Cosmology and cosmogony in a cyclic universe(Indian Academy of Sciences, 2007-04-26) Narlikar, J. V.; Burbidge, G.; Vishwakarma, R. G.In this paper we discuss the properties of the quasi-steady state cosmological model (QSSC) developed in 1993 in its role as a cyclic model of the universe driven by a negative energy scalar field. We discuss the origin of such a scalar field in the primary creation process first described by F. Hoyle & J. V. Narlikar forty years ago. It is shown that the creation processes which take place in the nuclei of galaxies are closely linked to the high energy and explosive phenomena, which are commonly observed in galaxies at all redshifts. The cyclic nature of the universe provides a natural link between the places of origin of the microwave background radiation (arising in hydrogen burning in stars), and the origin of the lightest nuclei (H, D, He³ and He⁴). It also allows us to relate the large scale cyclic properties of the universe to events taking place in the nuclei of galaxies. Observational evidence shows that ejection of matter and energy from these centers in the form of compact objects, gas and relativistic particles is responsible for the population of quasi-stellar objects (QSOs) and gamma-ray burst sources in the universe. In the later parts of the paper we briefly discuss the major unsolved problems of this integrated cosmological and cosmogonical scheme – the understanding of the origin of the intrinsic redshifts, and the periodicities in the redshift distribution of the QSOs.Item Modeling repulsive gravity with creation(Indian Academy of Sciences, 2007-01-18) Vishwakarma, R. G.; Narlikar, J. V.There is a growing interest among cosmologists for theories with negative energy scalar fields and creation, in order to model a repulsive gravity. The classical steady state cosmology proposed by Bondi, Gold & Hoyle in 1948, was the first such theory which used a negative kinetic energy creation field to invoke creation of matter. We emphasize that creation plays a very crucial role in cosmology and provides a natural explanation to the various explosive phenomena occurring in local (z < 0.1) and extra galactic universe.We exemplify this point of view by considering the resurrected version of this theory – the quasi-steady state theory, which tries to relate creation events directly to the large scale dynamics of the universe and supplies more natural explanations of the observed phenomena. Although the theory predicts a decelerating universe at the present era, it explains successfully the recent SNe Ia observations (which require an accelerating universe in the standard cosmology), as we show in this paper by performing a Bayesian analysis of the data.Item QSSC re-examined for the newly discovered SNe Ia(World Scienti c Publishing Company, 2004-08-08) Vishwakarma, R. G.; Narlikar, J. V.We examine the possible consistency of the quasi-steady state model with the newly discovered SNe Ia. The model assumes the existence of metallic dust ejected from the SNe explosions, which extinguishes light travelling overlong distances. We fi nd that the model shows a reasonable fit to the data, which improves if one take account of the weak gravitational lensing e ffect of the SNe which have been observed on the brighter side.Item Inhomogeneities in the microwave background radiation interpreted within the framework of the quasi-steady state cosmology(American Astronomical Society, 2003-03-01) Narlikar, J. V.; Vishwakarma, R. G.; Hajian, Amir; et al.We calcul ate the expected angular power spectrum of the temperature fluctuations in the microwave background radiation (MBR) generated in the quasi–steady state cosmology (QSSC ). The paper begins with a brief description of how the background is produced and thermalized in the QSSC. We then discuss within the framework of a simple model the likely sources of fluctuations in the background due to astrophysical and cosmological causes. Power spectrum peak s at l=6–10, 180–220, and 600–900 are shown to be respectively related in this cosmology to curvature effects at the last minimum of the scale factor, clusters, and groups of galaxies. The effect of clusters is shown to be related to their distribution in space as indicated by a toy model of structure formation in the QSSC. We derive and parameterize the angular power spectrum using six parameters related to the sources of temperature fluctuations at three characteristic scales. We are able to obtain a satisfactory fit to the observational band power estimates of the MBR temperature fluctuation spectrum. Moreover, the values of the best-fit parameters are consistent with the range of expected values .Item Interpretations of the accelerating universe(Astronomical Society of the Pacific, 2002-10-26) Narlikar, J. V.; Vishwakarma, R. G.; Burbidge, G.It is generally argued that the present cosmological observations support the accelerating models of the universe, as driven by the cosmological constant or `dark energy'. We argue here that an alternative model of the universe is possible which explains the current observations of the universe. We demonstrate this with a reinterpretation of the magnitude-redshift relation for Type Ia supernovae, since this was the test that gave a spurt to the current trend in favour of the cosmological constant.Item Dynamics of ejection from galaxies and the variable mass hypothesis(World Scientific Publishing Company, 2001-05-29) Narlikar, J. V.; Vishwakarma, R. G.; Banerjee, Shyamal K.Increasing numbers of active galaxies with signi cant alignments of quasars are being observed. It is the purpose of this paper to explore ejection dynamics of these quasars using the variable mass hypothesis (VMH) originally discussed by Narlikar and Das in 1980. According to the VMH quasars are ejected from parent galaxies initially with zero rest mass which grows through a Machian interaction. The intrinsic redshift of the quasar steadily decreases as its mass grows, but always remains in excess of the redshift of the galaxy. The ultimate aim of this hypothesis is to quantitatively relate the observed ordering of redshifts of ejected quasars, with separation from the galaxy, their intrinsic redshifts and the age of the evolutionary stage of the ejecta.