相关论文: Constraining Brans-Dicke Parameter Using Gravitati…
Einstein's General Relativity theory simplifies dramatically in the limit that the spacetime dimension D is very large. This could still be true in the gravity theory with higher derivative terms. In this paper, as the first step to study…
Four dimensional gravity in the low energy limit of a higher dimensional theory has been expected to be a (generalized) Brans-Dicke theory. A subtle point in brane world scenarios is that the system of four dimensional effective…
We derive the conditions for a non-equatorial eccentric bound orbit to exist around a Kerr black hole in two-parameter spaces: the energy, angular momentum of the test particle, spin of the black hole, and Carter's constant space ($E$, $L$,…
We re-express gravitational wave results in terms of post-Newtonian parameters. Using these expressions, and some simplifying assumptions, we compute that in a favorable case, i.e. a ten solar-mass black hole spiraling in to a 10^6…
By making an intuitive choice for the single-particle density of a system of N self-gravitating particles, without any source for the radiation of energy, we have been able to calculate the binding energy of the system by treating these…
A gravitational extension of Dirac's "Extensible model of the electron" is presented. The Dirac bubble, treated as a 3-dim electrically charged brane, is dynamically embedded within a 4-dim $Z_{2}$-symmetric Reissner-Nordstrom bulk. Crucial…
We explore a new mechanism of slowing down the rotation of neutron stars via accretion of millicharged dark matter. We find that this mechanism yields pulsar braking indices that can be substantially smaller than the standard $n\sim 3$ of…
The gravitational lensing of relativistic and nonrelativistic neutral massive particles in the black-bounce-Schwarzschild black hole spacetime is investigated in the strong deflection limit. Beginning with the explicit equations of motion…
The model of d5 higher derivative (HD) gravity admitting Schwarzschild--anti de Sitter Black Hole (S-AdS BH) as exact solution is considered. The surface counterterms are added to the complete action, they are fixed by the condition of…
This paper is intended to investigate the luminosity due to accretion of gas in supermassive black holes (SMBHs) in the center of quasars, using a brane-world scenario naturally endowed with extra dimensions, whereon theories formulated…
Quasi-periodic oscillations (QPOs) observed in a giant flare of a strongly magnetized neutron star (magnetar), are carrying crucial information for extracting the neutron star properties. The aim of the study is to constrain the mass and…
The measured rotation velocity profiles of mature spiral galaxies are successfully described with a gravitational model consisting of a thin axisymmetric disk of finte radius. The disk is assumed uniformly thin but with variable radial mass…
We investigate the possibility of generating sizeable dipole radiations in relativistic theories of gravity. Optimal parameters to observe their effects through the orbital period decay of binary star systems are discussed. Constraints on…
We investigate the quantum origin of the primordial cosmological gravitational waves in the Brans-Dicke theory. We compute the number of gravitons $N_k$ produced during inflation and the observables: power spectrum $P_T$, spectral index…
We use Big Bang Nucleosynthesis (BBN) data in order to impose constraints on the exponent of Barrow entropy. The latter is an extended entropy relation arising from the incorporation of quantum-gravitational effects on the black-hole…
This thesis describes a numerical study of binary boson stars within the context of an approximation to general relativity. The approximation we adopt places certain restrictions on the dynamical variables of general relativity (conformal…
The Brans Class I solution in Brans-Dicke gravity is a staple in the study of gravitational theories beyond General Relativity. Discovered in 1961, it describes the exterior vacuum of a spherical Brans-Dicke star and is characterized by two…
We present a new technique to constrain the gravitational potential of a galaxy from the observed stellar mass surface density alone under a number of assumptions. It uses the classical Eddington Inversion Method to compute the phase-space…
We study D- and DF-strings in a D3${\bar {\rm D}}3$ system by using Dirac-Born-Infeld type action. In the presence of an electric flux from the transverse direction, we discuss gravitating thick D-string solutions of a spatial manifold,…
We make a detailed study of boson star configurations in Jordan--Brans--Dicke theory, studying both equilibrium properties and stability, and considering boson stars existing at different cosmic epochs. We show that boson stars can be…