Non-Gaussianity from Excited Initial Inflationary States
  We study squeezed limit $f_{NL}$ generation by excited initial inflationary
states in a model independent way. We restrict "excited" to mean a Bogoliubov
transformation of the Bunch Davies state. We simultaneously impose the
constraints that the observable power spectrum is nearly scale invariant over
at least three decades and that the observable modes today be subhorizon at the
beginning of inflation while not causing significant backreaction. We show that
most excited initial inflationary states for single field inflationary models
with negligible superhorizon evolution do not produce an observable squeezed
limit $f_{NL}$. The case in which one mode is in the Bunch Davies state while
the other two modes are in an excited state with $0.01<|\beta_k|\leq0.1$ may
generate a squeezed limit $f_{NL}$ which is detectable with future experiments.
