scholarly journals Congruence kinematics in conformal gravity

2019 ◽  
Vol 65 (3) ◽  
pp. 261
Author(s):  
Mohsen Fathi
Keyword(s):  
Radial Solution ◽  
Conformal Gravity ◽  
Weyl Theory ◽  
Integral Curves ◽  
Theory Of Gravity ◽  
Raychaudhuri Equations

In this paper we calculate the kinematical quantities possessed by Raychaudhuri equations, tocharacterize a congruence of time-like integral curves, according to the vacuum radial solution of Weyl theory of gravity. Also the corresponding flows are plotted for denfinite values of constants.

scholarly journals OBSERVABLE QUANTITIES IN WEYL GRAVITY

2011 ◽  
Vol 26 (32) ◽  
pp. 2403-2410 ◽  
Author(s):  
MOHAMMAD REZA TANHAYI ◽  
MOHSEN FATHI ◽  
MOHAMMAD VAHID TAKOOK
Keyword(s):  
Cosmological Constant ◽  
Linear Approximation ◽  
Hubble Parameter ◽  
Current State ◽  
Weyl Gravity ◽  
Weyl Theory ◽  
Theory Of Gravity ◽  
The Universe ◽  
Good Agreement

In this paper, the cosmological "constant" and the Hubble parameter are considered in the Weyl theory of gravity, by taking them as functions of r and t, respectively. Based on this theory and in the linear approximation, we obtain the values of H0 and Λ0 which are in good agreement with the known values of the parameters for the current state of the universe.

scholarly journals Corners of gravity: the case of gravity as a constrained BF theory

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Remigiusz Durka ◽  
Jerzy Kowalski-Glikman
Keyword(s):  
Cosmological Constant ◽  
Boundary Structure ◽  
Schwarzschild Solution ◽  
Bf Theory ◽  
Theory Of Gravity

Abstract Following recent works on corner charges we investigate the boundary structure in the case of the theory of gravity formulated as a constrained BF theory. This allows us not only to introduce the cosmological constant, but also explore the influence of the topological terms present in the action of this theory. Established formulas for charges resemble previously obtained ones, but we show that they are affected by the presence of the cosmological constant and topological terms. As an example we discuss the charges in the case of the AdS-Schwarzschild solution and we find that the charges give correct values.

Black hole solutions and thermodynamics in the infinite derivative theory of gravity

2021 ◽  
Vol 103 (4) ◽  
Author(s):  
Yong Xiao ◽  
Yong Chen ◽  
Haiyuan Feng ◽  
Chenrui Zhu
Keyword(s):  
Black Hole ◽  
Theory Of Gravity ◽  
Infinite Derivative ◽  
Black Hole Solutions

scholarly journals Plastic forming processes of transverse non-homogeneous composite metallic sheets

2021 ◽  
Vol 11 (1) ◽  
pp. 294-302
Author(s):  
Gal Davidi
Keyword(s):  
Inner Core ◽  
Plastic Material ◽  
Radial Solution ◽  
Algebraic Differential Equation ◽  
Forming Process ◽  
Perfectly Plastic ◽  
Plastic Forming ◽  
Validity Limit ◽  
Significant Achievement

Abstract In this work an analysis of the radial stress and velocity fields is performed according to the J 2 flow theory for a rigid/perfectly plastic material. The flow field is used to simulate the forming processes of sheets. The significant achievement of this paper is the generalization of the work by Nadai & Hill for homogenous material in the sense of its yield stress, to a material with general transverse non-homogeneity. In Addition, a special un-coupled form of the system of equations is obtained where the task of solving it reduces to the solution of a single non-linear algebraic differential equation for the shear stress. A semi-analytical solution is attained solving numerically this equation and the rest of the stresses term together with the velocity field is calculated analytically. As a case study a tri-layered symmetrical sheet is chosen for two configurations: soft inner core and hard coating, hard inner core and soft coating. The main practical outcome of this work is the derivation of the validity limit for radial solution by mapping the “state space” that encompasses all possible configurations of the forming process. This configuration mapping defines the “safe” range of configurations parameters in which flawless processes can be achieved. Several aspects are researched: the ratio of material's properties of two adjacent layers, the location of layers interface and friction coefficient with the walls of the dies.

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