Research Papers (JVN)
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Item Black hole physics in globally hyperbolic space-times(Indian Academy of Sciences, 1982-02-16) Joshi, P. S.; Narlikar, J. V.The usual definition of a black hole is modified to make it applicable in a globally hyperbolic space-time. It is shown that in a closed globally hyperbolic universe the surface area of a black hole must eventually decrease. The implications of this breakdown of the black hole area theorem are discussed in the context of thermodynamics and cosmology. A modified definition of surface gravity is also given for non-stationary universes. The limitations of these concepts are illustrated by the explicit example of the Kerr-Vaidya metric.Item Anomalous redshifts and the variable mass hypothesis(Korean Astronomical Society, 1997-05-18) Narlikar, J. V.There are several observations of extragalactic objects that do not appear to be consistent with the cosmological hypothesis that their redshifts arise from the expansion of the universe. These phenomena are looked at in a spacetime framework that is wider in its scope than general relativity. This framework directly incorporates the Machian notion of intertia and is conformally invariant. The consequence of this approach is that the mass of a particle may not stay constant. Two alternative viewpoints are presented to explain how large redshifts could arise from emission of radiation by particles of low masses.Item Energy distribution for a spherically symmetric isolated system in general relativity(Plenum Publishing Corporation, 1996-07-09) Petrov, A.N.; Narlikar, J. V.The problems of the tolal energy and quasilocalenergy density or an isolated spherically symmetric static system in general relativity (GR) are considered with examples of some exact suintions. The field formulation of GR dereloped earlier hy L. P. Grishchuk. el al. (1984). in ihe framework of which all the dynamical fields, including the gravitation field, are considered in a fixed background spacetime is used intensively. The exact Schwarzschild and Reissner Nordstrom solutions are investigated in detail, and the results are compared with those in the recent work by J. D. Brown and J. W. York. Jr. (1993) as well as discussed with respect to the principle of nonlocalization of the gravitational energy in GR. Those examples are illustrative and simple because the background is selected as Minkowski spacetime and, in fact, the field configurations are studied in the framework of special relativity. It is shown that some problems of the Schwarzschild solution which are difficult to resolve in the standard geometrical framework of GR are resolved in the framework of the field formulation.Item Quasi-steady state cosmology(University of South Africa, 1994-01-22) Narlikar, J. V.Because of a number of unsatisfactory features of the standard hot big bang cosmology, it is argued that there is a case for exploring alternative approaches to cosmology. The approach described here attempts to relate the large scale features of the universe to the basic phenomenon of creation of matter. This theory, called the quasi steady state cosmology (QSSC), begins with a field heoretic description of matter creation within the framework of general relativity. A scalar field C of zero restmass but negative energy and stresses interacts with matter at the instants of creation thereby preserving the law of conservation of the universe expanding at an overall exponential rate along with cycles of expansion and contraction with shorter time scales. It is argued that such a solution arises from mini-creation events taking place near the event horizons of highly collapsed massive objects. The now familiar phe- nomena like QSOs, AGN , radio sources, etc. are the manifestations of matter creation in such events. These events arc cophased and the oscillations occur because of feedback between the creation process and the expansion of space. In this way he cosmology is seen to be related to high energy astrophysics in a very direct way. The QSSC can explain the abundances of light nuclei and the microwave background, the observed large scale features of the universe like the m — z relation, the source count, the angular size-redshift relation, as well as the observed distribution of the ages of galaxies. This work gives a brief review of these properties of the quasi steady state cosmology.Item Does a possible laboratory observation of a frequency anisotropy of light result from a non-zero photon mass m?(Elsevier Science Publishers, 1991-04-08) Narlikar, J. V.; Pecker, J. C.; Vigier, J. P.Assuming a priori the existence of a non-zero photon rest-mass m1>0 and justifying this assumption, we can predict the exisence of an anisotropy in velocity and frequency of light in the direction ofthe apex ofthe 3 K background cosmic radiation field. Since this frequency shift can now be tested in the laboratory, it is important to improve the precision ofthese measurements in Order to check our predictions. Its possible confirmation implies indeed the definition of an absolute evolution parameter in the rest frame Σ0 of this 3 K background microwave radiation.Item Quantum conformal cosmology(Israel Physical Society, 1990-07-28) Narlikar, J. V.This article discusses an approach to quantum gravity via path integrals. The more conventional approaches look upon general relativity as a field theory. It is argued here that relativity in fact seeks to replace the standard notion of force fields by the concept of non-Euclidean geometry. Any quantization program should take due note of this fundamental aspect. Here it is shown that considerable insight can be gained into the complexities of quantum gravity by a more limited but exact approach that quantizes the conformal degree of freedom only. It is shown, for example, that the likelihood of the universe having originated from a spacetime singularity is vanishingly small. Other interesting consequences of the approach are briefly described.