Origin of the Universe as a quantum tunneling event

We present a nonsingular model of cosmogenesis in which the Universe arises as a result of quantum-mechanical barrier penetration. The Universe is described throughout its evolution by a Friedmann-Robertson-Walker (FRW) metric, and the matter distribution by a perfect fluid, whose equation of state is chosen so as to allow the tunneling to occur. Cosmic evolution proceeds in three stages; an initial static spacetime configuration tunnels into a "fireball" state in which particle creation occurs. As the fireball expands, particle creation ends, and the Universe enters the "post-big-bang" epoch of adiabatic expansion. We find that within the context of the FRW ansatz, only a spatially closed universe may originate in this manner. Implications of this creation scheme and possible generalizations are discussed. As a by-product of this investigation we find that the evolution of the Universe is described by a Gell-Mann—Low equation with the $\beta$ function specified by the equation of state.