Eur. Phys. J. C (2016) 76: 91
https://doi.org/10.1140/epjc/s10052-016-3932-0

Regular Article - Theoretical Physics

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

¹ Leung Center for Cosmology and Particle Astrophysics, National Taiwan University, Taipei, 10617, Taiwan
² SLAC National Accelerator Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA, 94305, USA
³ Institute of Astrophysics, Central China Normal University, Wuhan, 430079, China

^* e-mail: innocent.yeom@gmail.com

Received: 14 January 2016
Accepted: 3 February 2016
Published online: 20 February 2016

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 can cross the cosmological constant boundary phenomenologically.