Model of a multiverse providing the dark energy of our universe

Abstract: It is shown that the dark energy presently observed in our universe can be regarded as the energy of a scalar field driving an inflation-like expansion of a multiverse with ours being a subuniverse among other parallel universes. A simple model of this multiverse is elaborated: Assuming closed space geometry, the origin of the multiverse can be explained by quantum tunneling from nothing; subuniverses are supposed to emerge from local fluctuations of separate inflation fields. The standard concept of tunneling from nothing is extended to the effect that in addition to an inflationary scalar field, matter is also generated, and that the tunneling leads to an (unstable) equilibrium state. The cosmological principle is assumed to pertain from the origin of the multiverse until the first subuniverses emerge. With increasing age of the multiverse, its spatial curvature decays exponentially so fast that, due to sharing the same space, the flatness problem of our universe resolves by itself. The dark energy density imprinted by the multiverse on our universe is time-dependent, but such that the ratio $w{=}\varrho/(c^2p)$ of its mass density and pressure (times $c^2$) is time-independent and assumes a value $-1{+}\epsilon$ with arbitrary $\epsilon{>}0$. $\epsilon$ can be chosen so small, that the dark energy model of this paper can be fitted to the current observational data as well as the cosmological constant model.