Phantom Universe from CPT Symmetric Qft

We develop a generalization of semiclassical field theory for the case of non-Hermitian Hamiltonians with CPT symmetry and construct a classical cosmological, scalar-field based model describing a smooth transition from ordinary dark energy to the phantom one. Our model arises from a Lagrangian with a complex potential leading to a non-trivial vacuum with real vacuum energy. Equivalence with models involving two scalar fields one of which is phantom-like is discussed.