Symmetron Inflation
  We define a new inflationary scenario in which inflation starts naturally
after the Big Bang when the energy density drops below some critical value. As
a model, we use recently proposed symmetron field whose effective potential
depends on the energy density of the environment. At high densities, right
after the Big Bang, the potential for the symmetron is trivial, and the field
sits in equilibrium at the bottom of the potential. When the density drops
below some critical value, the potential changes its shape into a symmetry
breaking potential, and the field starts rolling down. This scenario does not
require any special initial conditions for inflation to start. We also
construct a concrete model with two fields, i.e. with symmetron as an inflaton
and an additional scalar field which describes the matter content in the early
universe. For the simplest coupling, the amplitude and shape of the power
spectrum are the same as in the single field slow-roll inflation.
