An introduction to inflation and cosmological perturbation theory
  This article provides an introductory review of inflation and cosmological
perturbation theory. I begin by motivating the need for an epoch of inflation
during the early stages of the radiation dominated era, and describe how
inflation is typically achieved using scalar fields. Then, after an overview of
linear cosmological perturbation theory, I derive the equations governing the
perturbations, and outline the generation of the scalar and the tensor
perturbations during inflation. I illustrate that slow roll inflation naturally
leads to an almost scale invariant spectrum of perturbations, a prediction that
seems to be in remarkable agreement with the measurements of the anisotropies
of the cosmic microwave background. I describe the constraints from the recent
observations on some of the more popular models of inflation. I conclude with a
brief discussion on the status and certain prospects of the inflationary
paradigm.
