118474507
INTERIOR REISSNER-NORDSTR ¨ OM METRIC ON SPHEROIDAL SPACE-TIMES
The collapse of a spherically symmetric distribution of matter to a point singularity can be avoided when the matter is accompanied by the presence of some charge, the gravitational attraction then being counterbalanced by the repulsive Coulombian force field in addition to the pressure gradient. The problem of determining analytic interior solutions to the coupled Einstein-Maxwell equations corresponding to charged perfect fluid spheres in equilibrium has therefore received considerable attention [1–8]. Vaidya and Tikekar [9] and Tikekar [10] have shown that spheriodal space-times (i.e. space-times whose t = const sections have the geometry of a 3-spheroid immersed in a 4-dimensional Euclidean space) admit solutions to the Einstein field equations describing the interior space-times of spherical superdense stars in equilibrium. This approach has also been extensively examined by Maharaj and Leach [11] and Mukherjee, et al. [12]. These studies indicate an intimate relationship between the spheroidal geometry of the physical space and the distribution of matter in equilibrium of astrophysical significance. Since the gravitational collapse of spherical distributions of matter can be averted by the presence of electric charge, there arises a pertinent question of whether space-times endowed with spheroidal geometry can accommodate the presence of an electric charge. In this paper it is shown that the ansatz prescribing the spheroidal geometry to the 3-space associated with
119358995
A unified approach to charged-fluid distributions in general relativity
SummaryThe exact solutions for a charged perfect fluid are derived. The general analytical solution obtained depends on an arbitrary function of one of the space coordinates. As an illustration of the proposed method, the solution for a charged infinite plane has been obtained.
122637587
Bianchi type III and Kantowski-Sachs cosmological models in Lyra geometry
The cosmological models for Bianchi type III and Kantowski-Sachs space-time within the framework of Lyra geometry are obtained. The physical behaviour of the models have also been discussed.
116059635
Viscous cosmological models with particle creation in Brans-Dicke theory
The effect of bulk viscosity on the evolution of the spatially flat Friedmann-Robertson-Walker models in the context of open thermodynamical systems, which allow particle creation, is analyzed within the framework of Brans-Dicke theory. Particle creation and bulk viscosity have been considered as separated irreversible processes. To accommodate the viscous pressure and creation pressure, which is associated with creation of matter out of gravitational field, the energy-momentum tensor is modified. Dynamical behaviour of the models have been discussed.
121611284
Some cosmological models with constant deceleration parameter
SummaryBerman (1983) presented a law of variation of Hubble’s parameter that yields constant deceleration parameter models of the Universe. In this paper, Robertson-Walker models have been studied in Einstein’s theory with cosmological term and in cosmological theory based on Lyra’s geometry. Some simple models have been obtained. The necessary relations in each model have been derived, considering a perfect fluid.
116888804
Bianchi type V and VI0 cosmological models in Lyra geometry
The Bianchi type V and VI0 models have been investigated in Lyra geometry in both the cases with the gauge function β is a time dependent and β=constant. The physical behaviour of these models has been discussed.
120347980
K-shell fluorescence yield of Cs
A new technique has been developed in the measurement of the K-shell fluorescence yield of cesium from the analysis of the sum peaks observed with a high resolution intrinsic Ge detector. The value found is ..omega../sub k/(Cs) = 0.896(16), which is in good agreement with the fitted value of Bambynek et al.
122026076
Role of nuclear dissipation and entrance channel mass asymmetry in pre-scission neutron multiplicity enhancement in fusion-fission reactions
Pre-scission neutron multiplicities are measured for ${}^{12}\mathrm{C} + {}^{204}\mathrm{Pb}$ and ${}^{19}\mathrm{F} + {}^{197}\mathrm{Au}$ reactions at laboratory energies of 75\char21{}95 MeV for the $^{12}\mathrm{C}$ beam and 98\char21{}118 MeV for the $^{19}\mathrm{F}$ beam. The chosen projectile-target combinations in the present study lie on either side of the Businaro-Gallone mass asymmetry (${\ensuremath{\alpha}}_{\mathrm{BG}}$) and populate the $^{216}\mathrm{Ra}$ compound nucleus. The dissipation strength is deduced after comparing the experimentally measured neutron yield with the statistical model predictions which contains the nuclear viscosity as a free parameter. Present results demonstrate the combined effects of entrance channel mass asymmetry and the dissipative property of nuclear matter on the pre-scission neutron multiplicity in fusion-fission reactions.
1536642
Montage: a grid portal and software toolkit for science-grade astronomical image mosaicking
Montage is a portable software toolkit to construct custom, science-grade mosaics that preserve the astrometry and photometry of astronomical sources. The user specifies the dataset, wavelength, sky location, mosaic size, coordinate system, projection, and spatial sampling. Montage supports massive astronomical datasets that may be stored in distributed archives. Montage can be run on both single- and multi-processor computers, including clusters and grids. Standard grid tools are used to access remote data or run Montage on remote computers. This paper describes the architecture, algorithms, performance, and usage of Montage as both a software toolkit and a grid portal.
54082430
Ring and jet-like structures and two-dimensional intermittency in nucleus–nucleus collisions at 200AGeV/c
Abstract We have investigated the presence of ring and/or jet-like structures in the angular emission of secondary charged mesons (shower tracks) coming out of 16O–Ag/Br and 32S–Ag/Br interactions, each at an incident momentum of 200 A GeV / c . Nuclear photographic emulsion technique has been used to collect the experimental data. The experimental results have been compared with the results simulated by Monte Carlo method. The analysis indicates presence of ring and jet-like structures in the experimental data beyond statistical noise. This kind of jet structure is expected to give rise to a strong two-dimensional ( 2 d ) intermittency. The self-affine behaviour of 2d scaled factorial moments (SFM) has therefore been investigated and the strength of 2d intermittency has been determined. For each set of data the 2d results have been compared with the respective one-dimensional ( 1 d ) intermittency results.
120176685
Intermittency and multiplicity moments of charged particles produced in 32S–Ag/Br interaction at 200 A GeV/c
The nature of nonstatistical fluctuations in the density distribution of singly charged particles produced in 32S–Ag/Br interactions at an incident momentum of 200 A GeV/c has been investigated. With the help of the nuclear photographic emulsion technique, the data were collected, and using different statistical methods of multiplicity moments these data have been analysed in terms of intermittency and fractal properties of one- and two-dimensional phase space distributions. Wherever possible, experimental results have been compared with the results obtained in other similar heavy-ion-induced experiments, as well as with those obtained from simulated events of the Lund Monte Carlo code FRITIOF. In some cases events simulated by generating (pseudo)random numbers have also been used for the purpose of comparison. The investigation shows the presence of weak intermittency in one dimension (1D) that is consistent with self-similarity in the density distribution. In two dimensions (2D), anisotropy in the distributions along longitudinal and transverse phase space variables indicates that self-affinity, rather than self-similarity in the distributions, is responsible for the observed behaviour. From the analysis of factorial correlators and oscillatory multiplicity moments, the presence of a few-particle short-range correlation has also been established. In almost all cases, the simulated interactions fail to replicate the experimental results.