Speaker
Description
In this talk we make a case for considering alternatives to the Bunch-Davies vacuum state for quantizing inflaton perturbations. The choice of vacuum state of a (free) quantum field theory in a generic (spatially flat) Friedmann-Robertson-Walker spacetime is unavoidably ambiguous, with two physically viable vacua potentially behaving drastically differently at small momentum. We consider a specific class of vacuum states, known as States of Low Energy (SLE), and show that the associated mode functions will always have a universal small momentum expansion in all Friedmann-Robertson-Walker spacetimes. This expansion also entails that the SLE two-point function for a massless theory will be infrared finite. Finally, we present the primordial power spectrum corresponding to the SLE, and find that it matches the Bunch-Davies power spectrum at high momentum, while showing relative power suppression of low momentum modes.
