Reionization Through the Lens of Percolation Theory

Understand

The reionization of intergalactic hydrogen has received intense theoretical scrutiny over the past two decades.

• Here, we approach the process formally as a percolation process and phase transition.
• Using semi-numeric simulations, we demonstrate that an infinitely-large ionized region abruptly appears at an ionized fraction of ~0.1 and quickly grows to encompass most of the ionized gas: by an ionized fraction of 0.3, nearly ninety percent of the ionized material is part of this region.
• Throughout most of reionization, nearly all of the intergalactic medium is divided into just two regions, one ionized and one neutral, and both infinite in extent.