Cosmological Measures without Volume Weighting

TL;DR

This paper critiques volume weighting in cosmological measures, proposing volume averaging as an alternative to avoid Boltzmann brain dominance and questioning the implications of eternal inflation on universe volume.

Contribution

It introduces volume averaging as a new approach to the cosmological measure problem, challenging the traditional volume weighting method.

Findings

Volume averaging can prevent Boltzmann brain dominance.

It may eliminate the need for infinite universe volume in eternal inflation.

Suggests a paradigm shift in cosmological measure approaches.

Abstract

Many cosmologists (myself included) have advocated volume weighting for the cosmological measure problem, weighting spatial hypersurfaces by their volume. However, this often leads to the Boltzmann brain problem, that almost all observations would be by momentary Boltzmann brains that arise very briefly as quantum fluctuations in the late universe when it has expanded to a huge size, so that our observations (too ordered for Boltzmann brains) would be highly atypical and unlikely. Here it is suggested that volume weighting may be a mistake. Volume averaging is advocated as an alternative. One consequence may be a loss of the argument that eternal inflation gives a nonzero probability that our universe now has infinite volume.