Sharif Digital Repository

This thesis introduces a fast and accurate two-phase reservoir flow simulation procedure. The speed up is achieved by an upscaling technique where coarsening is applied to the detailed geological reservoir descriptions. This process results to two major error sources affecting the simulation accuracy significantly. The homogenization error is appeared when coarse scale data, such as equivalent permeability, is calculated from the available fine grid model information. It is shown that the error can be reduced adjusting coarse grid (non-uniform Cartesian) distribution. For the first time in this study, the grid distribution optimization is done based on “vorticity” map. In particular, the... 

There has been a growing interest in studying asymptotically AdS space times given the AdS/CFT conjecture. Among different models finding the one which decribes broader phenomena is important.The importance of a dynamical metric stems from the fact that one can see thermalization in its dual description. We introduce a dynamical metric and study apparent horizon formation and energy evolution as well. We plot its appparent horizion curve and show that it aproaches the static limit within our numerical accuracy. We then review quasi-normal modes of this space time  

Near Horizon Extremal Geometries (NHEG), are geometries which may appear in the near horizon region of the extremal black holes. These geometries have SL(2;R)U(1)n isometry, and constitute a family of solutions to the theory under consideration. In the first part of this report,their thermodynamic properties are reviewed, and their three universal laws are derived. In addition, at the end of the first part, the role of these laws in black hole thermodynamics is presented. In the second part of this thesis, we review building their classical phase space in the Einstein-Hilbert theory. The elements in the NHEG phase space manifold are built by appropriately chosen coordinate transformations of... 

In this manuscript we used the method of coset construction to describe theories of spontaneous symmetry breaking. The mathematical details are included in chapter 2. The utility of the method is that without any knowledge of the UV part of a theory we can construct IR part by just knowing the symmetry breaking pattern. We used the method for some symmetry breaking patterns to construct general relativity, massive gravity and also some symmetry breaking patterns corresponding to conformal gravity  

The standard model of Cosmology (SM), based on Einstein’s theory of general relativity (GR), is the best model in describing the cosmic-scale observations. In galactic scales, however, galactic dynamics show a discrepancy between the observed luminous mass and the predicted value from the theory. Two approaches are suggested to eliminate this inconsistency: assuming the existence of dark matter within the context of GR, or modifying the theory of gravity in galactic scales, like MOND or MOG. In this thesis, we study the spherical collapse and the formation of shell galaxies in MOG, in comparison with SM. We introduce the action and the field equations of MOG and the equation of motion of a... 

In this thesis, inspired by foundational discussions about the concepts of energy and entropy in the gravitational theory, we study the definitions of these concepts and the roles they play in that theory. The definitions considered in this thesis are derived from canonical formalism. To this end, first of all, the variational principle and the canonical structure in the gravitational theory, especially in situations where the spacetime is bounded, is carefully studied and the boundary and corner actions as well as the canonical structure on the boundaries in three cases of non-null, null and general boundaries are derived. Based on this study, two canonical approaches, namely the... 

The purpose of this study is to investigate the effect of radiation pressure on accretion disks. The radiation density causes the separation of electrons from ions which leads to the creation of an internal electric dipole. In this study Radiation density is calculated using the Eddington limit. Afterwards radiation pressure is calculated with the use of collisions between photons and electrons in the plasma. Collisions are assumed to happen only between photons and electrons, due to the larger cross section of electrons compared to protons. The mentioned assumption causes the creation of an electric dipole and with it an internal electric field. The separation of the charges is assumed to... 

The physical description of particles states in the quantum theory are characterized by means of theirs mass and spin. The inertial and gravitational properties of mass are already well known in mechanics and gravitation theories as well as their quantum counterparts. In spite of mass, the inertial and gravitational properties of intrinsic spin are not studied that much.In this thesis we review the inertial and gravitational properties of intrinsic spin. Initially we explore the general procedure to formulate Dirac equation in arbitrary curved spacetime. Then we write Dirac equation in Kerr spacetime to draw physical conclusions about the interaction of Dirac particles with the Kerr...