Spontaneous Creation of Inflationary Universes and the Cosmic Landscape

TL;DR

This paper explores gravitational instantons in string theory that could explain the spontaneous emergence of inflationary universes, proposing a new wavefunction approach that favors inflationary vacua over others.

Contribution

It introduces a modified Hartle-Hawking wavefunction in string theory, providing a principle to select our universe's vacuum and analyzing quantum tunneling probabilities to various string vacua.

Findings

Preferred tunneling to inflationary universes over small cosmological constant universes.

Proposes a mechanism for stabilizing extra dimensions during inflation.

Suggests a new wavefunction approach incorporating decoherence effects.

Abstract

We study some gravitational instanton solutions that offer a natural realization of the spontaneous creation of inflationary universes in the brane world context in string theory. Decoherence due to couplings of higher (perturbative) modes of the metric as well as matter fields modifies the Hartle-Hawking wavefunction for de Sitter space. Generalizing this new wavefunction to be used in string theory, we propose a principle in string theory that hopefully will lead us to the particular vacuum we live in, thus avoiding the anthropic principle. As an illustration of this idea, we give a phenomenological analysis of the probability of quantum tunneling to various stringy vacua. We find that the preferred tunneling is to an inflationary universe (like our early universe), not to a universe with a very small cosmological constant (i.e., like today's universe) and not to a 10-dimensional uncompactified de Sitter universe. Such preferred solutions are interesting as they offer a cosmological mechanism for the stabilization of extra dimensions during the inflationary epoch.