‎the object of the present paper is to study spacetimes admitting‎ ‎quasi-conformal curvature tensor‎. ‎at first we prove that a quasi-conformally flat spacetime is einstein‎ ‎and hence it is of constant curvature and the energy momentum tensor of such a spacetime satisfying‎ ‎einstein's field equation with cosmological constant is covariant constant‎. ‎next‎, ‎we prove that if the perfect...

in order to present a quantitative indicator for the onset of instability, in this paper, the critical points of a stratified gravitational flow on a slope are found and analyzed. these points are obtained by means of the solution of the two-dimensional navier-stokes equations via the standard arakawa-c finite-difference method. results show that in the marginal richardson numbers, the critical...

‎The object of the present paper is to study spacetimes admitting‎ ‎quasi-conformal curvature tensor‎. ‎At first we prove that a quasi-conformally flat spacetime is Einstein‎ ‎and hence it is of constant curvature and the energy momentum tensor of such a spacetime satisfying‎ ‎Einstein's field equation with cosmological constant is covariant constant‎. ‎Next‎, ‎we prove that if the perfect flui...

Involving the Ricci curvature and the squared mean curvature, we obtain basic inequalities for different kind of submaniforlds of a Sasakian space form tangent to the structure vector field of the ambient manifold. Contrary to already known results, we find a different necessary and sufficient condition for the equality for Ricci curvature of C-totally real submanifolds of a Sasakian space form...

potential field images obtained in potential field data measurements are suitable tools for mineral and hydrocarbons resources explorations. these images consist of different anomalies which in many cases are contaminated with noise. the horizontal location of the boundaries of potential field anomaly sources is of interest in potential field interpretation. however, the edge of potential field...

the coordinate transformation allows the exact calculation of some electrode configurations. in this paper the prolate spherical coordination transformation is used to calculate the field of a hyperboloiderod against plan electrode. the exact field is caculated using two new parameters: 1) electrodes spacing and 2) the radius of curvature of the tip of the rod electrode. the partial discharge i...

We argue that space-time properties are not absolute with respect to the used frame of reference as is to be expected according to ideas of relativity of space and time properties by Berkley Leibnitz Mach Poincaré. From this point of view gravitation may manifests itself both as a field in Minkowski space-time and as space-time curvature. If the motion of test particles is described by the Thir...

Pseudo Ricci symmetric real hypersurfaces of a complex projective space are classified and it is proved that there are no pseudo Ricci symmetric real hypersurfaces of the complex projective space CPn for which the vector field ξ from the almost contact metric structure (φ, ξ, η, g) is a principal curvature vector field.