Zhang, XF (reprint author), Chinese Acad Sci, Inst High Energy Phys, POB 918-4, Beijing 100049, Peoples R China.
In the framework of a single scalar field quintom model with higher derivative, we construct in this Letter a dark energy model of which the equation of state (EOS) w crosses over the cosmological constant boundary. Interestingly during the evolution of the universe w < -1 happens just for a period of time with a distinguished feature that w starts with a value above -1, transits into w < -1, then comes back to w > -1. This avoids the big-rip jeopardy induced by w < -1. (c) 2006 Elsevier B.V. All rights reserved.