Relaxing to Three Dimensions

TL;DR

This paper introduces the relaxation principle, a cosmological selection mechanism, to explain why our universe has three spatial dimensions, showing that certain branes dominate during evolution.

Contribution

It proposes a new cosmological selection principle and applies it to explain the observed number of spatial dimensions via brane dominance.

Findings

Universe tends to be dominated by 3-branes and 7-branes

The relaxation principle favors certain vacua during cosmological evolution

Provides a potential explanation for the observed 3D space

Abstract

We propose a new selection principle for distinguishing among possible vacua that we call the "relaxation principle". The idea is that the universe will naturally select among possible vacua through its cosmological evolution, and the configuration with the biggest filling fraction is the likeliest. We apply this idea to the question of the number of dimensions of space. We show that under conventional (but higher-dimensional) FRW evolution, a universe filled with equal numbers of branes and antibranes will naturally come to be dominated by 3-branes and 7-branes. We show why this might help explain the number of dimensions that are experienced in our visible universe.