Noise-Induced Inflation

We consider a closed Friedmann-Robertson-Walkeruniverse driven by the backreaction from a massless,non-conformally coupled quantum scalar field. We showthat the backreaction of the quantum field is able to drive the cosmological scale factor over thebarrier of the classical potential so that if theuniverse starts near zero scale factor (initialsingularity) it can make the transition to anexponentially expanding de Sitter phase with a probabilitycomparable to that from quantum tunneling processes. Theemphasis throughout is on the stochastic nature ofbackreaction, which comes from the quantum fluctuations of the fundamental fields.