  We present a simple, exact and self-consistent cosmology with a
phenomenological model of quantum creation of radiation due to decay of the
scalar field. The decay drives a non-isentropic inflationary epoch, which exits
smoothly to the radiation era, without reheating. The initial vacuum for
radiation is a regular Minkowski vacuum. The created radiation obeys standard
thermodynamic laws, and the total entropy produced is consistent with the
accepted value. We analyze the difference between the present model and a model
with decaying cosmological constant previously considered.
