Quantum inflaton dynamics - art. no. 027301

We show that the quantum dynamics of a real scalar field for a large class of potentials in the symmetric Gaussian state, where nonperturbative quantu m contributions are taken into account, can be described equivalently by a two-dimensional nonlinear dynamical system with a definite angular momentum [U(1) charge of a complex theory]. A proposal is put forward that the symm etric Gaussian state with a nearly minimal uncertainty and a large quantum fluctuation, as an initial condition, naturally explains most of the essent ial features of the early stage of the inflationary universe. [S0556-2821(9 8)02024-4].