نتایج جستجو برای: einstein
تعداد نتایج: 26538 فیلتر نتایج به سال:
we classify the paracontact riemannian manifolds that their rieman-nian curvature satisfies in the certain condition and we show that thisclassification is hold for the special cases semi-symmetric and locally sym-metric spaces. finally we study paracontact riemannian manifolds satis-fying r(x, ξ).s = 0, where s is the ricci tensor.
for a given riemannian manifold (m,g),it is an interesting question to study the existence of a conformal diffemorphism (also called as a conformal transformation) f : m ! m such that the metric g? = fg has one of the following properties: (i)(m; g?) has constant scalar curvature. (ii)(m; g?) is an einstein manifold.
A time-like unit vector field is used to generalize Einstein's gravity. The resulting theory, called the Einstein-aether theory, consists of a minimal coupling between an aether field and gravity. Inspired by the Bopp-Podolsky electrodynamics, which is well-known for removing the singularity at the point charge, we generalized the Einstein-aether theory by adding such a higher order self-intera...
In this paper we study curvature properties of semi - symmetric type of totally umbilical radical transversal lightlike hypersurfaces $(M,g)$ and $(M,widetilde g)$ of a K"ahler-Norden manifold $(overline M,overline J,overline g,overline { widetilde g})$ of constant totally real sectional curvatures $overline nu$ and $overline {widetilde nu}$ ($g$ and $widetilde g$ are the induced metrics on $M$...
The application of “Modified Einstein Procedure” is recommended by the Specialized Committee on Sediment, Iranian Ministry of Energy. However, this method has not been applied to any river in the country. It is the purpose of this study to investigate the total sediment load of the Karun and Karkheh rivers at Ahwas and Hamidieh stations. The graphical calculations of the method are very complic...
We define an elliptic equation for Hermitian metrics which is related to the Einstein condition. Solutions to this equation are closely related to Kähler-Einstein metrics, and are automatically Kähler-Einstein when a certain non-positive condition is satisfied by c1(M). Given this, a natural flow equation arises taking Hermitian metrics to Kähler metrics. We prove short time existence and regul...
N(k)-quasi Einstein manifolds are introduced and studied.
We define an elliptic equation for Hermitian metrics which is related to the Einstein condition. Solutions to this equation are closely related to Kähler-Einstein metrics, and are automatically Kähler-Einstein when a certain non-positive condition is satisfied by c1(M). Given this, a natural flow equation arises taking Hermitian metrics to Kähler metrics. We prove short time existence and regul...
We classify solvable Lie groups with a free nilradical admitting an Einstein left-invariant metric. Any such group is essentially determined by the nilradical of its Lie algebra, which is then called an Einstein nilradical. We show that among the free Lie algebras, there are very few Einstein nilradicals. Except for the one-step (abelian) and the two-step ones, there are only six (here f(m, p) ...
Riemannian Killing conserved currents are used to find the energy spectra of classical spinning particles moving around a spinning string in Einstein-Cartan (EC) theory of gravity. It is shown that a continuos spectrum is obtained for planar open orbits while a discrete spectrum is obtained for circular planar orbits. A spin-spin effect between the spin of the test particle and the spin of the ...
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