Aspects of de-Sitter Conjectures, Inflation and Axions

Abstract

In this thesis we study three interesting ideas in Particle Physics and Cosmology: de-Sitter conjectures, some aspects of Inflation and Axions as Dark matter. The de-Sitter conjectures are statements about consistency of Effective Field theories with Gravity. Effective Field Theories play a crucial role in describing physics at low energies. Thus, constraining the space of possibles EFTs by various Ultra Violets (UV) consistency requirements have been a very active field of research for many years. The “Swampland program” is one such example which tries to find the EFTs which can be completed into quantum gravity in the UV. This program has recently gained impetus because of a quantitative proposal ( “The de-Sitter Conjecture”) on what the scalar potential of a theory coupled to gravity must satisfy. This original proposal was subsequently revised to a “Refined de Sitter Conjecture” based on the entropy of de-Sitter space and the distance conjecture. In Master’s thesis, we study these consequences in Particle Physics and Cosmology, in particular in the context of Inflation, In the final part of the thesis, we also study the role of Axions in Cosmology in particular as Dark matter using the Misalignment mechanism.