The Study of Quantum Effects in Early Universe

Rostami, Abasat | 2019

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 52001 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Golshani, Mehdi; Taghizadeh Firouzjaee, Javad
  7. Abstract:
  8. In this thesis, we study two important quantum effects at deSitter spacetime and using the Schrödinger field theory, the power spectrum of massive non-interacting, minimally coupled scalars in a fixed de Sitter background would be obtained. To calculate the N-point function in Schrödinger field theory, the ”in-in” formalism is extended in the Friedmann- Lemaître-Robertson-Walker (FLRW) universe. This formalism in such picture would have a crucial role for evaluating the correlation functions of those quantum states naturally written in Schrödinger picture. We compute the three-point function for primordial scalar field fluctuation in the single field inflation by this in-in formalism. The results are the same as the three-point function in the Heisenberg picture. Then, we study the primary entanglement effect on the decoherence of fields reduced density matrix which are in interaction with other fields or independent mode functions. One finds out that the existence of entanglement could couple dynamical equations coming from Schrödinger equation. We show that the primary entanglement has a significant role in decoherence of the system quantum state. We derive the relation between two vacuum states which their mode functions are transformed by the entangled transformation in Schrödinger picture. We discuss thatthe entanglement parameter should be a time dependent parameter and only in the first order of the entanglement parameter perturbation, it turns out to be a constant
  9. Keywords:
  10. Field Theory Schrodinger Picture ; Two-point Function ; Friedmann-Robertson-Lemaitre-Walker (FRLW) Space-Time ; Three-point Function ; Decoherence ; Entanglement ; Density Matrix

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