Spontaneous Creation of Inflationary Universes and the Cosmic Landscape

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 (or a higher dimensional supercritical) uncompactified de Sitter universe. Some solutions are interesting as they offer a cosmological mechanism for the stabilization of extra dimensions during the inflationary epoch.

Is brane inflation eternal?

“…We like to find out how nature selects one vacuum versus another vacuum, that is, why our particular vacuum is chosen. There needs to be a mechanism to pick out a particular vacuum in the string landscape dynamically, like the Hartle-Hawking wave-function of the universe [42] and its improved version [43,44,45], or the Hawking-Turok instanton [46]. Since cosmological data strongly suggests that our universe has gone through an inflationary epoch, we have to understand how this particular inflationary universe, that is, the one that evolves to our today's universe, is selected.…”

Dark Energy

“…For example, Firouzjahi, Sarangi and Tye [133,134] brings the decoherence effect to the quantum creation of universe, and found the preferred classical universe is born at string scale, which is good for inflationary cosmology. As another approach, Hartle, Hawking and Hertog [135,136] argues that from the Bayesian point of view, the quantum creation probability should multiply the spatial volume factor to get the observed probability.…”

Why the Universe started from a low entropy state

“…In [4,5] we argued that a landscape picture must, in fact, be expected of any theory of initial conditions. The hope would then be that a superselection rule emerges from the quantum dynamics whereby the Universe would find itself driven to choose a unique vacuum state which could be computed from the requirement that it is the most probable state the Universe can access starting from ''nothing'', [5][6][7][8][9].…”

“…This analysis can also be tied into current efforts [8,15] to select appropriate vacua from the landscape of string vacua. We do this by taking the landscape as the configuration space for the wavefunction of the Universe so that the landscape minisuperspace can be thought of as the phase space of the initial conditions for the universe.…”