Multi-Stream Inflation in a Landscape
  There are hidden observables for inflation, such as features localized in
position space, which do not manifest themselves when only one inflation
trajectory is considered. To address this issue, we investigate inflation
dynamics in a landscape mimicked by a random potential. We calculate the
probability for bifurcation of the inflation trajectory in multi-stream
inflation. Depending on the shape of the random bumps and the distance between
bumps in the potential, there is a phase transition: on one side of the
critical curve in parameter space isocurvature fluctuation are exponentially
amplified and bifurcation becomes very probable. On the other side bifurcation
is dominated by a random walk where bifurcations are less likely to happen.
