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Non-Gaussian Primordial Perturbations and Inflationary Models

Mirzatuny, Nareg | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 45285 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Mansouri, Reza; Khosravi, Shahram
  7. Abstract:
  8. 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 observable amount of non-Gaussianity in some models of Inflation. Having a vast number of Inflationary models, the amount and shape of non-Gaussianity can act as a distinguishing tool of different Inflationary models. Starting with the canonical Inflationary model, we will introduce and study in detail the standard process of calculating the primordial non-Gaussianty. To this end we study perturbation theory, ADM formalism, 3rd order action and in-in formalism. In the second part of the thesis we will study primordial non-Gaussianity in the context of Large Scale Structure. We will show that the bias parameter can have a scale dependent part due to primordial non-Gaussiantiy. Next, introducing f(R) gravity as a possible candidate to late time acceleration of the Universe, we will study growth index in these theories which can also introduce a new scale dependence in our theory of Cosmology.
    Finally, we will study the simultaneous effect of scale dependent bias and modified theory of gravity in matter power spectrum and some other cosmological observables
  9. Keywords:
  10. Cosmology ; Structure Formation ; Inflation ; Universe Large-Scale Structure ; Nongaussianity

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