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Heavy Modes In the Multifield Inflationary Models

Manouchehri Kousha, Hamed | 2017

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50242 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Abolhassani, Ali Akbar
  7. Abstract:
  8. In the second half of the 20th century, the standard cosmology was encountered some problems like flatness problem and horizon problem. The inflation theory proposed by Alan Guth in the 1980s, not only solved these problems but also predicted some primordial fulctuations for the universe that as a source for the fluctuations of cosmic microwave background, could explain our observations.The fluctuations predicted by simple inflationary models, are Gaussain. Although we have not found a valid observational result suggesting Non-Gaussianity in the primordial fluctuations so far, but these simple single scalar field inflationary models, are very specific. So it is very probable that in the furture some observations, like large Non-Gaussianity effects, will force us to use some more complex models, like multifield models.In this thesis after introducing standard cosmology, perturbation theory , inflation theory and deriving their main equations in the first three chapters; we discuss the concept of Non-Gaussianity in the fourth chapter and calculate in details the two-point function and bispectrum for a simple inflationary model. Finally, in the fifth chapter we discuss the multifield inflationary models, and specially discuss a model with three fields supposing the heaviness of two modes
  9. Keywords:
  10. Nongaussianity ; Early Universe ; Cosmology ; Inflationary Cosmology ; Cosmic Perturbation Theory ; Multi-Field Inflation

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