Anisotropic Compacts Stars on Paraboloidal Spacetime with Linear Equation of State

New exact solutions of Einstein's field equations (EFEs) by assuming linear equation of state, $p_r = \alpha (\rho - \rho_R)$ where $p_r$ is the radial pressure and $\rho_R$ is the surface density, are obtained on the background of a paraboloidal spacetime. By assuming estimated mass and radius of strange star candidate 4U 1820-30, various physical and energy conditions are used for estimating the range of parameter $\alpha$. The suitability of the model for describing pulsars like PSR J1903+327, Vela X-1, Her X-1 and SAX J1804.3658 has been explored and respective ranges of $\alpha$, for which all physical and energy conditions are satisfied throughout the distribution, are obtained.Comment: 10 pages, 12 figures, 1 tabl

21st Century Simulation: Exploiting High Performance Computing and Data Analysis

This paper identifies, defines, and analyzes the limitations imposed on Modeling and Simulation by outmoded paradigms in computer utilization and data analysis. The authors then discuss two emerging capabilities to overcome these limitations: High Performance Parallel Computing and Advanced Data Analysis. First, parallel computing, in supercomputers and Linux clusters, has proven effective by providing users an advantage in computing power. This has been characterized as a ten-year lead over the use of single-processor computers. Second, advanced data analysis techniques are both necessitated and enabled by this leap in computing power. JFCOM's JESPP project is one of the few simulation initiatives to effectively embrace these concepts. The challenges facing the defense analyst today have grown to include the need to consider operations among non-combatant populations, to focus on impacts to civilian infrastructure, to differentiate combatants from non-combatants, and to understand non-linear, asymmetric warfare. These requirements stretch both current computational techniques and data analysis methodologies. In this paper, documented examples and potential solutions will be advanced. The authors discuss the paths to successful implementation based on their experience. Reviewed technologies include parallel computing, cluster computing, grid computing, data logging, OpsResearch, database advances, data mining, evolutionary computing, genetic algorithms, and Monte Carlo sensitivity analyses. The modeling and simulation community has significant potential to provide more opportunities for training and analysis. Simulations must include increasingly sophisticated environments, better emulations of foes, and more realistic civilian populations. Overcoming the implementation challenges will produce dramatically better insights, for trainees and analysts. High Performance Parallel Computing and Advanced Data Analysis promise increased understanding of future vulnerabilities to help avoid unneeded mission failures and unacceptable personnel losses. The authors set forth road maps for rapid prototyping and adoption of advanced capabilities. They discuss the beneficial impact of embracing these technologies, as well as risk mitigation required to ensure success

Observations of stratospheric aerosols associated with the El Chichon eruption

Lidar observations of aerosols were carried out at Aberystwyth between Nov. 1982 and Dec. 1985 using a frequency doubled and frequency tripled Nd/Yag laser and a receiver incorporating a 1 m diameter in a Newtonian telescope configuration. In analyses of the experimental data attention is paid to the magnitude of the coefficient relating extinction and backscatter, the choice being related to the possible presence of aerosols in the upper troposphere and the atmospheric densities employed in the normalisation procedure. The aerosol loading showed marked day to day changes in early months and an overall decay was apparent only after April 1983, this decay being consistent with an e sup -1 time of about 7 months. The general decay was accompanied by a lowering of the layer but layers of aerosols were shown intermittently at heights above the main layer in winter months. The height variations of photon counts corrected for range, or of aerosol backscatter ratio, showed clear signatures of the tropopause. A strong correlation was found between the heights of the tropopause identified from the lidar measurements and from radiosonde-borne temperature measurements. A notable feature of the observations is the appearance of very sharp height gradients of backscatter ratio which seem to be produced by differential advection

A simple toy model for effective restoration of chiral symmetry in excited hadrons

A simple solvable toy model exhibiting effective restoration of chiral symmetry in excited hadrons is constructed. A salient feature is that while physics of the low-lying states is crucially determined by the spontaneous breaking of chiral symmetry, in the high-lying states the effects of chiral symmetry breaking represent only a small correction. Asymptotically the states approach the regime where their properties are determined by the underlying unbroken chiral symmetry.Comment: This is the published version of this paper. Note that the title has changed from earlier versions as has the abstract. The emphasis is slightly different from previous versions but the essential physical content is the sam