# Ghost Inflation

We propose a new scenario for early cosmology, where an
inflationary de Sitter phase is obtained with a ghost condensate.
The transition to radiation dominance is triggered by the ghost
itself, without any slow-roll potential. Density perturbations are
generated by fluctuations around the ghost condensate and can be
reliably computed in the effective field theory. The fluctuations
are scale invariant as a consequence of the de Sitter symmetries,
however, the size of the perturbations are parametrically
different from conventional slow-roll inflation, and the inflation
happens at far lower energy scales. The model makes definite
predictions that distinguish it from standard inflation, and can
be sharply excluded or confirmed by experiments in the near
future. The tilt in the scalar spectrum is predicted to vanish
(n_s=1), and the gravity wave signal is negligible. The
non-Gaussianities in the spectrum are predicted to be observable:
the 3-point function is determined up to an overall O(1)
constant, and its magnitude is much bigger than in conventional
inflation, with an equivalent f_NL \simeq 100, not far from
the present WMAP bounds.

hep group
Last modified: Wed Sep 17 21:35:31 EDT 2003