Sharif Digital Repository

In present thesis, the effect of cosmological constant, Λ, in bending of light by spherical symmetric mass has been studied. At first we obtain the Schwarzschild-de Sitter solution as spherical symmetric solution of General relativity field equations with cosmological constant, without we suppose the solution is static. Then we obtain gravitational lens equation by considering the space geometry and we benefited from several approach to specify the contribution of cosmological constant to the deflection angle. Furthermore we put new upper bounds on the value of the lambda independently of cosmological constraints. Finally for study the contribution of lambda in gravitational lensing... 

Gravitational lensing affects not only the position and number of images of cosmic objects but also their shapes. In the so-called weak gravitational lensing effects related to shape of the cosmic objects are studied. These require high quality images and wide field of view. Because of technology development and production of multi-chip CCD cameras in recent decades, we are witnessing an increase in the number of projects using weak lensing techniques. Taking instrumental errors into account, the first step in weak lensing studies should be the proper data reduction to produce final images in which instrumental errors are removed and have sufficient precision to be processed. In This thesis... 

We have tried this for the first time to reperesent a comprehensive description of the evolution of a perfect fluid in inhomogeneous relativistic models.We solve Einstein equations using numerical methods.In this procedure we can evaluate the effect of pressure in perfect fluid evolution.Also we look at the behavior of the various horizons, and in the end we will present a cosmological model to a black hole  

Inflation is the leading paradigm for the theory of early universe and the mechanism for generating the seeds of perturbation in cosmic microwave background and large scale structure. In this thesis various aspects of primordial anisotropies and the effects of long mode during inflation are studied. There exist two powerful tools in studying the effects of super-horizon inflationary perturbations, namely, Maldacena’s consistency condition and Weinberg’s theorem. However, there are inflationary models, such as solid inflation and non-attractor inflation, which evade these theorems and in this thesis we study their consequences and features. At first we study statistical anisotropy in the... 

In the most cosmological models which already have putted forth, metric has a spherical symmetry; however, according to the galaxy’s shape is not a real approximation. In order to build a more acqurate model, by applying a particular conformal transformation on the static vacuum solution, we introduce a new metric which is axially symmetric and also it approaches to FLRW metric at space infinity. The cosmological model according to this metric has especial features;The solution we have found represent a spacetime which is axially symmetric although it leads to a spherically symmetric Einstein tensor. Therefore, we have found a solution of Einstein equations representing a spherically... 

Studing the Scattering Amplitudes has a crucial importance in Quantum Field Theory; and nowadays; there have been many progress in computing these observables: Scattering amplitudes respect the symmetries of a theory: However; it is possible for them to have more symmetries than ones can be seen from the lagrangian of the theory: On the other hand; Feynman diagrams which manifest the locality and unitarity of the theory are not applicable in these kind of theories; since for computing the easiest scattering amplitudes thousends of these diagrams must be computed: In this work; we are going to see using BCFW recursion relation and onshell diagrams how it is easy to compute the scattering... 

The concept of mass is considered as a fundamental concept in physics. There are, however, ambiguities in its definition in different areas of physics. Specifically, in general relativity we are facing many quasi-local mass definitions for structures leading to different numerical values for astrophysical objects. Our aim is to study the relevance of the concept of mass in astrophysics and cosmology. Astrophysicists use different mass concepts for different applications. We have studied all these defi- nitions and tried to find out how relevant they are. It seems the fundamental concept used in all these definitions is the energy density, which is a local concept and has a unique definition in general... 

Using a general relativistic model for structures in a cosmological background, we calculated the Geodesics within a structure such as a galaxy or a cluster of galaxies in order to obtain the velocity profile of stars or galaxies. The profile defines a Newtonian mass which is then compared to different local gravitational masses, such as Misner-Sharp, Liu-Ya and ... to see how different they are. In this project we used numerical methods for solving geodesics equations of LTB metric and Einstein’s field
equations.
 

In this work we investigate the propagattion of light in inhomogenous cosmic spacetime within general relativity framework. We use Lemaitr-Tolaman-Bondi metric for modeling inhomogenous spacetime. For investigation of gravitational lensing we need to solve geodesic equaions in this model. Beacuse of nonlinearity and complexity of these equations we should apply numerical methods. At first we used Runge-Kutta method with adaptive step size, but beacuse of stiffness of these equaions, the results of this method did not match to approximation methods for low deflection angles. So we try semi-implicit Rosenbrock method. Then for inspection of thin lens approximation for the first time; we... 

Galaxy clusters are the most massive virialized systems in the universe. Their studies provide crucial grasp on the galaxy formation and evolution, dark matter and its nature, cosmological parameters and large scale structure of the universe. Because of their significant role in cosmology, providing a catalogue of galaxy clusters in a wide range of spatial angle, mass and redshift seems vital. Galaxy cluster detection can be performed by various methods in a broad spectrum of electromagnetic radiation. Optical detection of galaxy clusters is of the most traditional and popular methods. Among optical algorithms, one of the most efficient is called Cluster Red Sequence (CRS) which applies the... 

In the era of precision cosmology it is desirable to know if the collapse of an overdensity region within a FRW cosmological model leads to a black hole similar to that of Schwarzschild. Even the simple question of an event horizon within a dynamical universe is not a trivial one. This subject of studying collapsing over-densities within an expanding universe is called ”cosmological black holes”. Our aim is to construct such a black hole in the simplest possible scenario and study its similarities and differences to the familiar Schwarzschild one in vacuum. Therefore questions of rotating or charged black holes are not dealt with in our work. We insist, however, that the solution is dynamic... 

The market demand of super heavy crude oil is very low due to its determinative both physical and chemical properties. Unfortunately existing refineries in Iran are not capable to refine this kind of crude oil. Marketing issues besides great price difference with other crude oil types leads us to find economical solution for optimal use of this national possession. About 70 percent of super heavy crude oil produced from Soroush and Norouz oil fields is un-refineable materials and to refine this heavy crude oil to refinery products like gasoline or gas oil a refinery with RFCC ( Residual Fluid Catalitic Cracking) technology must be made. Super high Technology and very heavy capital cost... 

The use of wind energy due to the clean and unlimited nature of this energy has received more attention and for this purpose, the types of wind turbines that mainly include; monopile turbines and jacket-based turbines; is used In this research project, it has been tried using criteria such as equal weight of structures with different bracing shapes and taking into account the normalized energy and redundancy factors of the platforms; An optimal structure that can achieve a better capacity curve with the same material cost, which includes ultimate stress and greater ductility, and along with all the above factors; The redundancy of the structure has also been considered to minimize the risk... 

This thesis is divided into two major parts. In the first half of the thesis we introduce and study primordial non-Gaussianity in the context of Inflationary Cosmology. Most recent cosmological observations indicate that Universe has experienced an inflationary phase during its very early moments of existence. Not only Inflation is a possible solution of FRW cosmology problems, but also it acts as the generator of all the structure in the Universe. According to standard Inflationary cosmology, the primordial fluctuations which are considered to be the seeds of the entire structure in the Universe are scale-invariant, adiabatic and Gaussian.However there is the possibility to have an... 

We study the fundamental and the photometric plane of a sample of 50 dwarf galaxies within the core of Coma cluster observed with DEIMOS on Keck II down to R-band luminosity of -15 Magnitudes. The Calcium triplet lines in the wavelength range between 7500 to 10,000 ˚A, allow us to obtain the velocity dispersion for the sample galaxies with high precision. We also performed a comprehensive error analysis to better estimate the uncertainties of this key observable. We also carried out a galaxy structure modeling using the ACS I-band images for a larger sample. We found larger velocity dispersions for fainter dwarfs than what expected from mass-luminosity trends of brighter Coma galaxies. In... 

Cosmic Inflation, invented by Alan Guth in 1980’s, solves the shortcomings of the Standard Cosmology such as the flatness, the horizon and the monopoles problems and provides the seeds of large scale structure formation. The quantum fluctuations which are produced during inflationary epoch are redshifted and transferred from Microscopic scales to Macroscopic universe. We can observe this macroscopic fluctuations both on the CMB surface and on large scale structures. Data from WMAP and Planck missions(CMB space Telescopes) suitably confirms the general predictions of single field inflationary scenarios but still people search for finding primordial gravitational waves from the B-Mode signal... 

Effective parameters on decolourization of Sumifix Black B or Reactive Black 5 (RB5) by the extracted peroxidase from Coprinus Cinereus NBRC 30628 in a bioreactor have been reviewed in this master thesis. These parameters were such as hydrogen peroxide concentration, pH of dye solution, enzymatic activity and hydraulic retention time. All of these parameters were optimized in such condition that enzyme solution was added to bioreactor at the initial time of reaction. Optimum concentration for hydrogen peroxide, pH, dye concentration, and hydraulic retention time in above mentioned condition of reactor were 96.1 mM, 8, 40 ppm, and 60 min, respectively. It is worth to note that the higher... 

Tin sulfide with an energy gap of about 1.1 ev is a semiconductor suitable for applications such as solar cells, lithium-ion batteries, photocatalysts and other semiconductor-based devices. There are several methods for synthesizing this semiconductor at the nanometer scale, among which the solvothermal method is an efficient, controllable and inexpensive method. By precisely controlling the parameters of this process, two-dimensional tin sulfide nanosheets with high purity and desirable morphology can be produced. In this research, tin sulfide has been synthesized by solvothermal / hydrothermal chemical method and its metallurgical properties have been studied. Effect of solvothermal... 

One of the main subjects that has been vastly studied recently, is the final fate of Black holes with Hawking radiation. Radiation of a black hole changes the black hole, thus horizons of the black hole will also have dynamics. For a radiating black hole the inward flux of matter and the flux of radiation are two important factors for determining black hole energymomentum tensor that determine dynamics of different kinds of horizons. Quantum flux calculation needs choosing a proper quantum state as vacuum for calculating the expectation value of energy-momentum tensor. In this thesis we have attempted to write a useful reference and we hope it could help the reader to prepare for studying... 

Compact Objects involve White Dwarfs,Neutron Stars and Black Holes which are formed from the gravitational collapse of main sequence stars after their nuclear fuel is finished.The special characteristic of all Compact Objects is that they are high density which requires a vast knowledge of nuclear physics with strong and weak interactions ,electromagnetic and numerical methods.we need general relativistic simulation of stars because the theories are simple and some are not in agreement with observations. studying of astro physical constraints on equation of state ,stability and cooling of Neutron Stars and pulsation of gravitational waves is needed nowadays. in first part of this thesis,we...