Cosmic eggs to relax the cosmological constant

TL;DR

This paper proposes a cosmological model where the universe originates from a 'cosmic egg', a compact, one-dimensional state, which dynamically relaxes the cosmological constant and leads to the emergence of our large, expanding universe.

Contribution

It introduces a novel mechanism involving cosmic eggs that naturally explains the smallness of the cosmological constant through quantum tunneling and initial conditions.

Findings

Cosmic eggs can evolve into higher-dimensional universes.

The model predicts a small positive cosmological constant.

Initial conditions from cosmic eggs can explain the vacuum energy value.

Abstract

In theories with extra dimensions, the cosmological hierarchy problem can be thought of as the unnaturally large radius of the observable universe in Kaluza-Klein units. We sketch a dynamical mechanism that relaxes this. In the early universe scenario we propose, three large spatial dimensions arise through tunneling from a 'cosmic egg', an effectively one-dimensional configuration with all spatial dimensions compact and of comparable, small size. If the string landscape is dominated by low-dimensional compactifications, cosmic eggs would be natural initial conditions for cosmology. A quantum cosmological treatment of a toy model egg predicts that, in a variant of the Hartle-Hawking state, cosmic eggs break to form higher dimensional universes with a small, but positive cosmological constant or quintessence energy. Hence cosmic egg cosmology yields a scenario in which the seemingly unnaturally small observed value of the vacuum energy can arise from natural initial conditions.