Can the Universe Create Itself?

The question of first-cause has troubled philosophers and cosmologists alike. Now that it is apparent that our universe began in a Big Bang explosion, the question of what happened before the Big Bang arises. Inflation seems like a very promising answer, but as Borde and Vilenkin have shown, the inflationary state preceding the Big Bang could not have been infinite in duration — it must have had a beginning also. Where did it come from? Ultimately, the difficult question seems to be how to make something out of nothing. This paper explores the idea that this is the wrong question — that that is not how the Universe got here. Instead, we explore the idea of whether there is anything in the laws of physics that would prevent the Universe from creating itself. Because spacetimes can be curved and multiply connected, general relativity allows for the possibility of closed timelike curves (CTCs). Thus, tracing backwards in time through the original inflationary state we may eventually encounter a region of CTCs — giving no first-cause. This region of CTCs may well be over by now (being bounded toward the future by a Cauchy horizon). We illustrate that such models — with CTCs — are not necessarily inconsistent by demonstrating self-consistent vacuums for Misner space and a multiply connected de Sitter space in which the renormalized energy-momentum tensor does not diverge as one approaches the Cauchy horizon and solves Einstein’s equations. Some specific scenarios (out of many possible ones) for this type of model are described. For example: a metastable vacuum inflates producing an infinite number of (Big-Bang-type) bubble universes. In many of these, either by natural causes or by action of advanced civilizations, a number of bubbles of metastable vacuum are created at late times by high energy events. These bubbles will usually collapse and form black holes, but occasionally one will tunnel to create an expanding metastable vacuum (a baby universe) on the other side of the black hole’s Einstein-Rosen bridge as proposed by Farhi, Guth, and Guven. One of the expanding metastable-vacuum baby universes produced in this way simply turns out to be the original inflating metastable vacuum we began with. We show that a Universe with CTCs can be stable against vacuum polarization. And, it can be classically stable and self-consistent if and only if the potentials in this Universe are retarded — which gives a natural explanation of the arrow of time in our universe. Interestingly, the laws of physics may allow the Universe to be its own mother.