Phantom of the Hartle-Hawking instanton: connecting inflation with dark energy

TL;DR

This paper explores how the Hartle-Hawking instanton framework can naturally produce a stable, non-singular phantom energy component that explains dark energy and allows the equation of state to cross the cosmological constant boundary.

Contribution

It introduces a novel connection between quantum cosmology instantons and quintom dark energy models, providing a theoretical basis for crossing the cosmological constant boundary.

Findings

Phantomness from instantons avoids big rip singularity.

Non-classicalized fields can embed into quintom models.

Wave function effects prevent perturbative instabilities.

Abstract

If the Hartle-Hawking wave function is the correct boundary condition of our universe, the history of our universe will be well approximated by an instanton. Although this instanton should be classicalized at infinity, as long as we are observing a process of each history, we may detect a non-classicalized part of field combinations. When we apply it to a dark energy model, this non-classicalized part of fields can be well embedded to a quintessence and a phantom model, i.e., a quintom model. Because of the property of complexified instantons, the phantomness will be naturally free from a big rip singularity. This phantomness does not cause perturbative instabilities, as it is an effect emergent from the entire wave function. Our work may thus provide a theoretical basis for the quintom models, whose equation of state (EoS) can cross the cosmological constant boundary (CCB) phenomenologically.