Spectrum of Cuscuton Bounce
  It has been recently shown that a cosmological bounce model based on Cuscuton
gravity does not have any ghosts or curvature instabilities. We explore whether
Cuscuton bounce can provide an alternative to inflation for generating near
scale-invariant scalar perturbations. While a single field Cuscuton bounce
generically produces a strongly blue power spectrum (for a variety of
initial/boundary conditions), we demonstrate that scale invariant entropy modes
can be generated in a spectator field that starts in adiabatic vacuum, and is
kinetically coupled to the primary field. Furthermore, our solution has no
singularity, nor requires an ad hoc matching condition. We also study the
generation of tensor modes (or gravitational waves) in Cuscuton bounce and show
that while they are stable, similar to other bounce models, the produced
spectrum is strongly blue and unobservable.
