Cosmological Probes of Physics Beyond the Standard Model

Abstract

The Standard Model (SM) of particle physics can explain a diverse variety of experimental observations. However, there remain multiple compelling reasons why we believe that the SM is not the final theory of the universe. In this thesis, we first briefly discuss some of those shortcomings of the SM, and then focus on ways in which cosmological observations can be used to probe theories beyond the SM. The primary probe we consider for this purpose is primordial non-Gaussianity (NG) of cosmological perturbations. We show that by precise studies of NG we can probe ultra-high energy gauge theories that might otherwise be energetically completely inaccessible to terrestrial experiments, by focusing first on (i) generic spontaneously broken Higgsed gauge theories, and then on, (ii) higher-dimensional Grand Unified Theories (GUTs). Building upon this, we also discuss a simple curvaton extension of the standard inflationary paradigm where strength of various NG signals can be orders of magnitude larger, and thus be easily accessible via observations in the coming decade.