Comments on matter collineations of plane symmetric, cylindrically symmetric and spherically symmetric spacetimes

Comments are made on some recently published papers on matter collineations of plane symmetric, cylindrically symmetric and spherically symmetric spacetimes

On the definition of matter collineations

It is shown that when the stress-energy tensor of a spacetime is diagonal and is written in the mixed form, its collineations admit infinite dimensional Lie algebras except possibly in the case when the tensor depends on all the spacetime coordinates. The result can be extended for more general second rank tensors

EVALUATING THE EFFECT OF INDUSTRIAL EFFLUENTS ON CHEMICAL COMPOSITION OF SOIL IN VILLAGE DINGI, DISTRICT HARIPUR

The present report is an outcome of research work conducted in Dingi village, District Haripur in 2012. The research aimed to assess and analyze the effects of industrial effluents on the soil fertility of the village, investigate contributing factors responsible for soil pollution and underlying causes creating the problems. Data analysis revealed that area had problems pertaining to water and soil quality. The key factors affecting soil fertility were the careless discharge of the untreated industrial effluents from Hattar Industrial Estate (HIE) into the natural stream passing through village. The results were compared with the soil standards set by the World Wide Fund for Nature (WWF) and European Committee Commission (ECC) and all of these were exceeding the permissible limits and affecting the soil fertility. The soils were found not fit for agriculture. The investigation highlighted the need to take some effective steps to manage the monitoring program set for checking of industries by the government according to set rules and regulation

Simulink based Analysis and Realization of Line Commutated Grid Tied Inverter for Renewable Energy Applications

Non-conventional energy resources are increasingly used to fulfill load demands. Before using such energy sources the very important thing is analysis at the basic level. This paper presents analysis and realization of line commutated grid tied inverter for renewable energy applications. The current-voltage and power-voltage characteristics of solar PV array changes as parameters like solar insolation and temperature changes. These characteristics are found and realized using MATLAB software. Line commutated inverters are discussed in this paper for grid interactive modes of operations

Gravitational wave scintillation by a stellar cluster

The diffraction effects on gravitational waves propagating through a stellar cluster are analyzed in the relevant approximation of Fresnel diffraction limit. We find that a gravitational wave scintillation effect - similar to the radio source scintillation effect - comes out naturally, implying that the gravitational wave intensity changes in a characteristic way as the observer moves.Comment: 9 pages, in press in IJMP

Conformal Ricci collineations of static spherically symmetric spacetimes

Conformal Ricci collineations of static spherically symmetric spacetimes are studied. The general form of the vector fields generating conformal Ricci collineations is found when the Ricci tensor is non-degenerate, in which case the number of independent conformal Ricci collineations is \emph{fifteen}; the maximum number for 4-dimensional manifolds. In the degenerate case it is found that the static spherically symmetric spacetimes always have an infinite number of conformal Ricci collineations. Some examples are provided which admit non-trivial conformal Ricci collineations, and perfect fluid source of the matter

Note on flat foliations of spherically symmetric spacetimes

It is known that spherically symmetric spacetimes admit flat spacelike foliations. We point out a simple method of seeing this result via the Hamiltonian constraints of general relativity. The method yields explicit formulas for the extrinsic curvatures of the slicings.Comment: 4 pages, to appear in PRD, reference added, typos correcte

Thermal instability in ionized plasma

We study magnetothermal instability in the ionized plasmas including the effects of Ohmic, ambipolar and Hall diffusion. Magnetic field in the single fluid approximation does not allow transverse thermal condensations, however, non-ideal effects highly diminish the stabilizing role of the magnetic field in thermally unstable plasmas. Therefore, enhanced growth rate of thermal condensation modes in the presence of the diffusion mechanisms speed up the rate of structure formation.Comment: Accepted for publication in Astrophysics & Space Scienc

Measurements of branching fractions, absolute transition probabilities and J-file sum rule for the 4p(5)5p -\u3e 4p(5)5s transitions array in neutral krypton

We present new results of transition rates for twenty two electric dipole transitions of neutral krypton associated with the 4p55p→4p55 s configurations-based levels covering the wavelength region from 500 to 1000 nm using a krypton filled hollow cathode discharge lamp coupled with a set of four miniature spectrometers. The branching fractions of various dipole allowed transitions were extracted using the observed line intensity ratios, whereas, the absolute values of the transition probabilities were deduced from the measured branching fractions in combination with the known lifetimes of the upper levels. The experimental data are in good agreement with that calculated in the intermediate angular momentum coupling scheme. In addition, line strengths for all the transitions have been extracted using the measured transition probabilities. The J-file sum rule was also tested for each level attached to the 4p55p→4p55 s configurations based on the recently measured and calculated normalized multiplet strengths