Inflationary Cosmology: Preparing the Theory to Match the Observations

Motivated by recent and forthcoming advances in observational cosmology, this program of research will develop the theoretical framework necessary for studying realistic inflationary models that can be tested against the wealth of available data. Specifically, it will focus on scenarios that predict potentially detectable levels of non-Gaussianity in the curvature perturbation as well as an observable gravitational wave background. Given the high energy scales associated with the very early universe, it is natural to develop inflationary scenarios within the context of higher-dimensional, unified field theories such as string/M-theory. We will study models of inflation where the accelerated expansion of our observable universe arises due to the motion of one or more `branes' propagating down a warped throat geometry of the higher dimensions. An analytical formalism will be developed that can account for the evolution of the adiabatic curvature perturbation due to isocurvature modes. This will be employed to calculate the three- and four-point correlation functions of the curvature perturbation. We will investigate how the level and scale-dependence of any non-Gaussianity that is generated depends on the nature of the initial vacuum state that is assumed. We will derive consistency equations between observable parameters that in principle could be employed to rule out or confirm different inflationary models. This offers the possibility of directly constraining the physics of the universe at energy scales that are inaccessible to any form of terrestrial experiment and will yield unique information on the origin, evolution and large-scale structure of the universe.