122564039
Bianchi type‐I cosmological models in Lyra’s geometry
Exact solutions are obtained for the anisotropic Bianchi type‐I model in normal gauge for Lyra’s geometry. The physical behavior of the models is examined in vacuum and in the presence of perfect fluids.
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.
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.
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.
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.
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.
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.
120167461
Anomalous behavior of the level density parameter in neutron and charged particle evaporation
The compound nucleus $^{76}\mathrm{Kr}*$ was populated at the excitation energy of $75\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$ and angular momentum of $39\ensuremath{\hbar}$ in fusion reactions with two complementary, mass-symmetric $(^{31}\mathrm{P}+^{45}\mathrm{Sc})$ and mass-asymmetric $(^{12}\mathrm{C}+^{64}\mathrm{Zn})$ entrance channels. The neutron evaporation spectra were measured and compared with the predictions of statistical model calculations using the transmission coefficients for the spherical nuclei in the inverse absorption channel, the rotating liquid drop model moment of inertia, and the normal systematic value of $A∕8$ for the level density parameter $a$. The results for the mass-asymmetric reaction are found to be consistent with the predictions of the statistical model calculations. However, for the mass-symmetric reaction $(^{31}\mathrm{P}+^{45}\mathrm{Sc})$, the experimental spectra are found to be harder than the theoretical neutron spectra and the statistical model calculations require a lower value of $A∕10$ for the parameter $a$ to reproduce the shape of the experimental spectra, indicating the neutron to be evaporated at higher temperature for the same excitation energy and angular momentum in symmetric system. According to the dynamical model, the formation time $(37\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}22}\phantom{\rule{0.3em}{0ex}}\mathrm{sec})$ of the compound nucleus for the symmetric $^{31}\mathrm{P}+^{45}\mathrm{Sc}$ system is significantly higher than that $(29\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}22}\phantom{\rule{0.3em}{0ex}}\mathrm{sec})$ for the asymmetric $^{12}\mathrm{C}+^{64}\mathrm{Zn}$ system. This may probably lead to the formation of a temperature-equilibrated dinuclear complex that may be responsible for neutron emission at higher temperature in the case of the symmetric system.
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.
121441857
Centrality dependence of nonstatistical fluctuation in single particle density distribution in S-32-Ag/Br interaction at 200A-GeV/c
Nonstatistical fluctuations in the density distribution of shower tracks coming out of 32S–Ag/Br interaction at an incident momentum of 200A GeV/c, have been characterized by using the intermittency and multifractality techniques. A sample of 32S–Ag/Br nuclear emulsion events has been partitioned into three subsamples with respect to the shower track multiplicity in such a way that one can roughly estimate the average centrality for each subsample. Thereby, the centrality dependence of a set of relevant intermittency and multifractal issues has been investigated.
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.