Effective Hamiltonian for non-minimally coupled scalar fields

Performing a relativistic approximation as the generalization to a curved spacetime of the flat space Klein-Gordon equation, an effective Hamiltonian which includes non-minimial coupling between gravity and scalar field and also quartic self-interaction of scalar field term is obtained.Comment: 4 page

Total Energy of Charged Black Holes in Einstein-Maxwell-Dilaton-Axion Theory

We focus on the energy content (including matter and fields) of the Møller energy-momentum complex in the framework of Einstein-Maxwell-Dilaton-Axion (EMDA) theory using teleparallel gravity. We perform the required calculations for some specific charged black hole models, and we find that total energy distributions associated with asymptotically flat black holes are proportional to the gravitational mass. On the other hand, we see that the energy of the asymptotically nonflat black holes diverge in a limiting case

Unified solutions of extended Gauss-Bonnet gravity

We study some scale factor power-law solutions of the field equations of the extended Gauss Bonnet gravity in the spatial FRW (Friedmann-Robertson-Walker) universe. We consider the lagrangian density given by F(R,G) = f (G) + R + αR2 which exhibits a modification comparing with the modified Gauss Bonnet gravity. After constructing the Friedmann equations and finding the power-law solution we obtain the real valued of our model describing a mechanism that shows transitions among three stages of the universe (inflation, deceleration, acceleration) in an unified way. In particular, in this unified solution we obtained an inflation model without using any scalar field description when α > 0, and also we verified our early time inflationary scenario using observational parameters, i.e. ns, r. Further, we research for the power-law solution of our model when the universe is in the phantom phase. Here, it is observed that the acceleration of the universe in phantom region is composed of two phases which congruent with the recent observations

A unified picture of cosmological entropy on apparent horizon in F(R, G) gravity

In this study, the validity of the generalized second law of thermodynamics (GSLT) has been investigated in F(R, G) gravity. We consider that the boundary of the universe is surrounded by an apparent horizon in the spatially flat Friedmann-Robertson-Walker (FRW) universe, and we take into account the Hawking temperature on the horizons. The unified solutions of the field equations corresponding to gravity theory have been applied to the validity of the GSLT frame, and in this way, both the solutions have been verified and all the expansion history of the universe has been shown in a unified picture

SPIN-1/2 PARTICLES IN TORSION GRAVITY WHEN A CONSTANT ELECTRIC FIELD IS PRESENT

In this work, we focus on the dynamics of Dirac particles in the presence of a constant electric field in a cosmological anisotropic universe. Instead of Einstein's theory of general relativity, we perform the calculations using the teleparallel theory of gravity which is also called as the torsion gravity. First, we found the exact solution of the teleparallel Dirac equation in an anisotropic Bianchi-I universe. Second, the harmonic oscillator behaviour of the solution and then the quantization of oscillation frequency had been discussed. Third, we investigated the spin precession of Dirac particles and dispute the axial-vector spin coupling term

The Momentum Four-Vector in Brans-Dicke Wormholes

This paper has been removed by arXiv administrators because it plagiarizes K.K. Nandi and Y.Z. Zhang, "An algorithm for generating rotating Brans-Dicke wormhole solutions," gr-qc/0606012; and Ragab M. Gad, "Energy and Momentum Densities Associated with Solutions Exhibiting Directional Type Singularities," gr-qc/0404108.Comment: This submission has been withdrawn by arXiv administrators due to inappropriate text reuse from external source