Constraining primordial perturbations on small scales

Abstract

The power spectrum of primordial curvature perturbations of our universe is very well measured on the largest observable length scales by cosmic microwave background (CMB) anisotropies. But on smaller scales, observational constraints on it are much weaker. In this thesis, we study various probes of primordial perturbations on small scales, namely CMB spectral distortions, primordial black holes, and secondary gravitational waves. We use these probes to constrain parametric forms of the primordial power spectrum. We investigate the dependence of these constraints on the shape of the spectrum. We then show how the same methodologies can be used to constrain an underlying model of inflation.