Tachyons in Inflation: Running and Spinodalling

Abstract: I investigate two corrections to the standard inflationary dynamics that may become important in the coming years. The first is explicit time dependence of the potential, which can naturally arise from a hidden sector undergoing a fast-roll phase, communicated to the inflaton through loop effects. The signature of such a scenario is an observable running of the spectrum, which would otherwise be almost precluded if inflation proves to be small field. Secondly, I investigate the influence of long wavelength modes on the dynamics of the background and perturbations, if the inflaton turns out to be tachyonic. A simple, self-consistent method of encapsulating effects is shown. This leads to important effects in several currently popular models.