Finite Canonical Measure for Nonsingular Cosmologies

TL;DR

This paper demonstrates that the canonical measure for certain nonsingular cosmological models is finite, with most solutions resembling rapid de Sitter expansion, and identifies conditions under which inflationary solutions have low measure.

Contribution

It provides a finite measure for nonsingular FRW cosmologies with a scalar field and positive cosmological constant, clarifying the measure distribution among different solution types.

Findings

Most measure concentrates on nearly de Sitter solutions with no inflation.

Solutions with large inflation have low measure when scalar energy density exceeds twice the cosmological constant.

Finite measure exists for models with a big bang and big crunch; only eternal expansion or contraction solutions have infinite measure.

Abstract

The total canonical (Liouville-Henneaux-Gibbons-Hawking-Stewart) measure is finite for completely nonsingular Friedmann-Lemaitre-Robertson-Walker classical universes with a minimally coupled massive scalar field and a positive cosmological constant. For a cosmological constant very small in units of the square of the scalar field mass, most of the measure is for nearly de Sitter solutions with no inflation at a much more rapid rate. However, if one restricts to solutions in which the scalar field energy density is ever more than twice the equivalent energy density of the cosmological constant, then the number of e-folds of rapid inflation must be large, and the fraction of the measure is low in which the spatial curvature is comparable to the cosmological constant at the time when it is comparable to the energy density of the scalar field. The measure for such classical FRW-Lambda-phi models with both a big bang and a big crunch is also finite. Only the solutions with a big bang that expand forever, or the time-reversed ones that contract from infinity to a big crunch, have infinite measure.