Graceful exit in quantum string cosmology

TL;DR

This paper develops a duality-symmetric quantum cosmology framework that allows smooth transitions between different cosmological phases, even across classical singularities, by solving a covariant Wheeler-De Witt equation.

Contribution

It introduces a duality-invariant Wheeler-De Witt equation in string cosmology and demonstrates finite quantum transition probabilities across classical singularities.

Findings

Finite quantum transition probability across singularities.

Operator ordering ambiguities are eliminated by duality symmetry.

Explicit examples of phase transitions between dual cosmological states.

Abstract

We write an O(d,d)-covariant Wheeler-De Witt equation in the ($d^2+1$)-dimensional minisuperspace of low-energy cosmological string backgrounds. We discuss explicit examples of transitions between two duality-related cosmological phases, and we find a finite quantum transition probability even when the two phases are classically separated by a curvature singularity. This quantum approach is completely free from operator ordering ambiguities as a consequence of the duality symmetries of the string effective action.