Informal Pizza Seminar

Cosmological effective actions and new physics in the CMB

Könraad Schalm

Columbia

We give a prescription for parametrizing the vacuum choice ambiguity in cosmological settings. An arbitrary boundary action is introduced torepresent the initial conditions. We discuss how the known vacuum choices, e.g. the Bunch-Davies vacuum, appear in the Lagrangian description. In this formalism, backreaction is manifestly under control for any choice of boundary conditions. All, moreover, will generically feel the influence of high-energy - Planck scale - physics through irrelevant (dimension four) boundary corrections. We derive an explicit expression for the power spectrum of inflationary density perturbations including the leading high energy corrections. The effect of high energy physics is linearly proportional to the Hubble radius H and the scale of new physics l = 1/M. Effects of such strength are potentially observable in future measurements of the cosmic microwave background. We conclude with an positive assessment on the phenomenological constraints and signatures of new physics in the CMB.