Quantum diffusion in sharp transition to non-slow-roll phase

Transitions between different inflationary slow-roll scenarios are known to provide short non-slow-roll periods with non-trivial consequences. We consider the effect of quantum diffusion on dynamics in a transition process. Using stochastic {\delta}N formalism, we follow detailed evolution noises through sharp modeled by Starobinsky potential, although some our results apply any transition. find how noise induced affects coarse-grained fields. then special case that potential is flat after It found particular obtain cannot drive inflaton past classically unreachable field values. By deriving characteristic function, also study tail behavior for distribution curvature perturbations {\zeta}, which decay faster than e^(-3{\zeta}).