A Note on Boltzmann Brains

TL;DR

This paper challenges traditional views on the conditions required for de Sitter vacuum decay rates to prevent Boltzmann brains from dominating, proposing that fundamental quantum gravity considerations may alter these criteria.

Contribution

It introduces a new perspective based on microscopic quantum gravitational degrees of freedom, suggesting decay rate conditions may be governed by Poincare recurrence rather than Boltzmann brain production.

Findings

Decay rate of de Sitter vacua may not need to satisfy Boltzmann brain production constraints.

Fundamental theory structure influences decay rate conditions.

Addresses Boltzmann brain production in Minkowski vacua.

Abstract

Understanding the observed arrow of time is equivalent, under general assumptions, to explaining why Boltzmann brains do not overwhelm ordinary observers. It is usually thought that this provides a condition on the decay rate of every cosmologically accessible de Sitter vacuum, and that this condition is determined by the production rate of Boltzmann brains calculated using semiclassical theory built on each such vacuum. We argue, based on a recently developed picture of microscopic quantum gravitational degrees of freedom, that this thinking needs to be modified. In particular, depending on the structure of the fundamental theory, the decay rate of a de Sitter vacuum may not have to satisfy any condition except for the one imposed by the Poincare recurrence. The framework discussed here also addresses the question of whether a Minkowski vacuum may produce Boltzmann brains.