Exploring Quantum Effects in Inflation

Abstract

Loop corrections in inflationary cosmology have received comparatively little attention, despite the fact that tree-level results can become unreliable when loop contributions dominate.So, in this thesis we compute the one-loop corrections to the power spectrum and bispectrum in a singlefield inflationary models, focusing on leading contributions in slow-roll parameters . Although,full evaluation of all possible diagrams still remains open due to technical challenges,we made some progress in calculating and understanding higher-order correction.We also present observations arising from the derivation of the perturbation action for inflaton fields. In addition, we review various methods for computing loop corrections and share insights gained during their evaluation.Finally, we also derive some perturbative constraint on the wavefunction coefficient in deSitter using the unitarity of Bunch-Davies S-matrix under some assumptions.