  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.
