Multiverse Understanding of Cosmological Coincidences

TL;DR

This paper proposes a multiverse-based framework to explain the coincidence of key cosmological timescales, deriving order-of-magnitude predictions for fundamental parameters by analyzing their statistical distributions near critical boundaries.

Contribution

It introduces a multiverse approach that links cosmological coincidences to parameter distributions near catastrophic boundaries, providing quantitative predictions for fundamental constants.

Findings

Predicts the cosmological constant and other parameters in terms of fundamental constants.

Shows the causal patch measure avoids runaway scenarios for key parameters.

Provides a systematic way to evaluate measure proposals in cosmology.

Abstract

There is a deep cosmological mystery: although dependent on very different underlying physics, the timescales of structure formation, of galaxy cooling (both radiatively and against the CMB), and of vacuum domination do not differ by many orders of magnitude, but are all comparable to the present age of the universe. By scanning four landscape parameters simultaneously, we show that this quadruple coincidence is resolved. We assume only that the statistical distribution of parameter values in the multiverse grows towards certain catastrophic boundaries we identify, across which there are drastic regime changes. We find order-of-magnitude predictions for the cosmological constant, the primordial density contrast, the temperature at matter-radiation equality, the typical galaxy mass, and the age of the universe, in terms of the fine structure constant and the electron, proton and Planck masses. Our approach permits a systematic evaluation of measure proposals; with the causal patch measure, we find no runaway of the primordial density contrast and the cosmological constant to large values.