The Entropic Landscape

TL;DR

This paper uses the entropic principle to make broad, testable predictions about the universe's properties, such as flatness and radiation background, consistent with current observations.

Contribution

It introduces a quantitative framework for the entire landscape using entropy production, deriving universal predictions applicable across diverse vacua.

Findings

Universe is flat and at vacuum domination onset

Relic radiation background matches observed cosmic infrared background

Predictions are robust across different vacua and particle physics models

Abstract

We initiate a quantitative exploration of the entire landscape. Predictions thus far have focused on subsets of landscape vacua that share most properties with our own. Using the entropic principle (the assumption that entropy production traces the formation of complex structures such as observers), we derive six predictions that apply to the whole landscape. Typical observers find themselves in a flat universe, at the onset of vacuum domination, surrounded by a recently produced bath of relativistic quanta. These quanta are neither very dilute nor condensed, and thus appear as a roughly thermal background. Their characteristic wavelength is of order the inverse fourth root of the vacuum energy. These predictions hold for completely arbitrary observers, in arbitrary vacua with potentially exotic particle physics and cosmology. They agree with observation: We live in a flat universe at the onset of vacuum domination, whose dominant entropy production process (the glow of galactic dust) has recently produced a radiation bath (the cosmic infrared background). This radiation is marginally dilute, relativistic, and has a wavelength of order 100 microns, as predicted.