Fate of the phantom dark energy universe in semiclassical gravity

The fate of the phantom dark energy universe in semiclassical gravity is investigated. Quantum corrections coming from massless fields conformally coupled with gravity are considered, to see if they can lead to avoidance of the big rip singularity, which shows up in a flat Friedmann-Robertson-Walker universe, filled with phantom dark energy and modeled by an equation of state of the form p=ωρ with ω<-1. The dynamics of the model are discussed for all values of the two parameters, named α>0 and β<0, which come from quantum corrections. It is concluded that, when -1<β3α<0, almost all solutions develop future singularities (the corresponding scale factor and energy density go down to zero in finite time). However, when -1>β3α, almost all solutions describe a universe bouncing infinitely many times (an oscillating universe). © 2011 American Physical Society.