COSMOLOGICAL PERTURBATIONS THEORY AND COSMIC MICROWAVE BACKGROUND OBSERVATION FOR INFLATION

• Main Author: Hikmawan, Getbogi
• Format: Dissertations
• Language: Indonesia
• Subjects: Fisika
• Online Access: https://digilib.itb.ac.id/gdl/view/46185
• Institution: Institut Teknologi Bandung

Standard cosmology had some problems in explaining the evolution of the universe, such as horizon problem and flatness problem. Inflation theory proposed to answer that problems, where the idea of inflation theory is that in the early time, our universe encountered a exponential expansion in a short period. Until recently, there are many models tried to give explanation about this phenomenon. However, the models existed are still become a speculation because of lack of observation data which can describe an inflation encountered by the universe. Therefore, there is a question arises, ”which model give the best explanation about inflation phenomenon?”. Inflation theory is developed because the standard model of the universe can not give any explanation about classical problems in cosmology. General relativity explains that the dynamics of our universe can be seen with Einstein equation. The left hand side of the Einstein equation describes the geometry of the universe, while the right hand side describes the matter fills the universe. The models considered can be constructed by two fundamental approach, that is to modify the right hand side of Einstein equation (or can be called as modified matter) or to modify the left hand side of Einstein equation (or can be called as modified gravity). The research conducted is analytic approach about the inflation model constructed from Horndeski theory, as the most general scalartensor theory, with cosmological perturbation (scalar and tensor). The result of analytical approach for non-perturbative and perturbative aspect from the model built show that inflation can happen naturally and stable in every perturbation mode. The stability of this model is studied from the dynamic equation for each perturbation mode. After that, spectral index of each perturbation mode from the model studied comply with observational data of cosmic microwave background.