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