, Volume 37, Issue 10, pp 1671-1674
Date: 13 Oct 2005

Does inflation provide natural initial conditions for the universe

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Abstract

If our universe underwent inflation, its entropy during the inflationary phase was substantially lower than it is today. Because a low-entropy state is less likely to be chosen randomly than a high-entropy one, inflation is unlikely to arise through randomly-chosen initial conditions. To resolve this puzzle, we examine the notion of a natural state for the universe, and argue that it is a nearly-empty spacetime. If empty space has a small vacuum energy, however, inflation can begin spontaneously in this background. This scenario explains why a universe like ours is likely to have begun via a period of inflation, and also provides an origin for the cosmological arrow of time.

This work was supported in part by the U.S. Dept. of Energy, the National Science Foundation, the NDSEG Fellowship, and the David and Lucile Packard Foundation.
Second Award in the 2005 Essay Competition of the Gravity Research Foundation. - Ed.