Sharif Digital Repository

In this thesis we perform the method for calculating primordial non- Gaussianity for a generic single-field inflationary model and compare the results of important models such as DBI inflation and slow roll inflation. Then, we will show how to extract potentially observable quantities from 3 point correlation functions of gauge invariant curvature perturbations, like the size and shape of non-Gaussianities. Then,we will review the effective field theory approach to inflation that allows us to unify all inflationary models and characterize high energy corrections to simple slow roll model. We use this approach to estimate the size of non-Gaussianities in various limit. Furthermore, we study... 

This thesis was conducted both numerically and experimentally. In the experimental investigations aqueous solutions of high molecular weight Carboxymethylcellulose (CMC) was used. The experimental set-up was composed of a glass syringe, and a piston which can easily move through the syringe. Different die with aspect ratio ranging from 5.25 to 28.8 can be attached to the syringe. The syringe then is filled with the CMC solution with different weight fractions. Then using a force exerting on the piston, the solution comes out of the die and exiting velocity was calculated from weight of CMC solution that exit from die in a definite time. High quality photographs were taken from extrudate... 

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... 

In this thesis the impact of inflation on urban household saving is investigated. For calculating sensitivity of saving respect to price changing of different groups of commodities, firstly we divided household cost to two separated groups of durable and nondurable and then by defining total income as summation of monetary and nonmonetary income of households, We consider saving as total income minuses nondurable consumption. Finally we estimated the “Extended Linear Expenditure System” model base on the prepared data. Since inflation is result of unequal changes in prices of goods and services, the approach of expenditure system allows us to assess unequal changes in prices for eight... 

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... 

Under volatile economic conditions, where inflation is high and market prices of materials, labor, and equipment change unexpectedly, construction cost rise. To avoid the disruption of work, the owner may be required to compensate the contractors in a way that the excess construction cost is partially or completely covered. This compensation should be provided to the contractors in a way that is authorized by the laws and regulations under which the contract is stipulated. Hence it is essential to have the proper mechanism, for sharing the burden of cost overruns caused by unforeseen economic conditions.
In Iran, the payment scheme for the majority of the medium-and large-scale contracts... 

We know the matter can curve the space-time according to the general theory of relativity. On the other hand Quantum Field Theory has been formulated in a flat space-time and we cannot use most of its techniques within a curved space-time. Formulating the Quantum Field Theory in curved space-time is important for various subjects in physics like early universe or black hole physics. We will review the formulating QFT in cosmological background and will look for observable consequences on Cosmological Microwave Background in this thesis  

In this project, in general, we have studied the particle production during and after the Inflation.Today, the Inflation is considered as a part of the standard model of cosmology and it solves so-called two cosmological problems: flatness and horizon problem. According to it,the universe after the inflation becomes supercool; however, the thing we observe today is in contradiction with this theory. The Reheating era is a time period in which the inflationary field gets to its minimum of potential and starts to socialite. Actually, here is the place in which the phenomenon of the particle production occurs. This period is called the Reheating era. therefore, it seems all particles which we... 

Inflation first introduced for solving the puzzles of the standard model of cosmology. Soon it became clear that this paradigm can provide a natural way for production of Initial conditions for the birth of large-scale structures: cosmological perturbations. But inflationary models are usually phenomenological models. They are constructed to solve the problems of the standard model of cosmology and explain the properties of cosmological fluctuations. Where do they come from? A property of a big family of inflationary models is the flatness of their potential. What would may be the cause of this flatness? . . .. In this thesis our purpose is searching about one probable field theoretic root... 

Temerature fluctuation of the Cosmic Microwave Background (CMB) is one of the key observebles of the modern cosmology. Today, it is widely believed that quantum fluctuation that are stretched to horizon scales during a period of acceleration expansion -- at the onset of evolution of the universe-- are responsible for these perturbations. In the simplest scenarios of the inflation, a scalar field is responsible for both nearly expansional expansion of the universe and the proimordial fluctuations. In this thesis, we investigate the models of inflation with an additional light degree of freedom. In particular, we employ the method of the Effective Field Theory to study the general structure... 

In the framework of quantum field theory, countless consistent theories can be constructed. However, it is understood that only a small subset of these theories can be consistently embedded in a theory of quantum gravity (QG). In string theory, as the best candidate for quantum gravity, there is a landscape of effective field theories (EFTs) which are descended from some compactification of extra dimensions. EFTs which are not derived from a compactification is said to belong to swampland. From a bottom-up point of view, the aim of the swampland program is to find a list of criteria which an EFT must respect so that it survives the swampland. The trans-Planckian censorship conjecture (TCC)... 

During the past 20 years, there has been an ever¬increasing interest in searching for anomalies or features beyond the standard scale¬invariant Gaussian spectrum of the CMB in the hope of finding signals of new physics. In this study, a new type of anomaly on the cosmic microwave background called the Inflationary Cherenkov effect is studied. By first simulating the expected effects and using machine learning methods such as convolutional neural networks, we obtain methods to detect this effect. Afterward, with the help of the detector, we study real data, namely temperature anisotropies of the CMB. Finally, we infer the speed of propagation of scalar field perturbations whose energy runs... 

Exponential expansion of the universe is an important issue in early-time and late-time cosmology . In the widely accepted standard model of cosmology, there are two assumed exponentially expanding phases , early-time inflationary phase and late-time dark energy phase . On the other hand, there are ideas from string theory that limit the possibility of constructing the de Sitter space, which are categorized in the Swampland program . In this work, we first examine no-scale models of de Sitter space in supergravity from the point of view of de Sitter conjectures . In this regard, we observe that satisfying these conjectures limits the parameter and field space and the trans-Planckian... 

Co-movement between inflation and nominal interest in response to an interest rate shock, dubbed neo-fisherianism, has been the subject of contentious debate since the advent of non-inflationary ZLB environment. We design an economic model rich with banking features to understand the economic responses to permanent and long-term interest rate shocks. We find that responses to a permanent positive interest rate shock depend on the monetary authorities’ speculation of the new long-term inflation rate, with the most probable outcome being a permanent increase in inflation. Responses to a long-term positive interest rate shock depict an increase and then decrease in inflation. We also discover...