Description
We discuss a model for a non-singular cosmic bounce in N=1 supergravity,
based on supergravity versions of the ghost condensate and cubic
Galileon scalar field theories. The cosmic bounce is preceded by an
ekpyrotic contracting phase which prevents the growth of anisotropies in
the approach to the bounce, and allows for the generation of
scale-invariant density perturbations that carry over into the expanding
phase of the universe. As the basis of this model, we develop a
formalism to write supergravity extensions of scalar field theories with
higher derivatives. We discuss the conditions required for the bounce to
be free of ghost excitations, as well as the tunings that are necessary
in order for the model to be in agreement with cosmological
observations. We show that all of these conditions can be met, and that
this model provides a proof-of-principle that non-singular bounces are
viable in supergravity, despite the fact that during the bounce the null
energy condition is violated.