Semiclassical cosmology with back reaction: the Friedmann-Schrodinger equation and inflation

We propose and study a semi-classical cosmological system akin to the Newton-Schr"odinger equation where matter field evolution is determined by time dependent Schr"odinger equation. The resulting dynamics is one where the scale factor self-consistently informs the quantum evolution of the scalar field wave function via the Friedmann equation. We study various potentials, and show that for each case, inflation arises naturally, without fine-tuning, for arbitrary initial wave functions for the scalar field. Furthermore, due to zero-point quantum fluctuations of the scalar field, the equation of state $P=-\rho$ arises dynamically at late times for all initial states and potentials.