Null Energy Condition and Dark Energy Models

Null Energy Condition (NEC) requires the equation of state (EoS) of the universe $w_u$ satisfy $w_u\geq-1$, which implies, for instance in a universe with matter and dark energy dominating $w_u=w_m\Omega_m+w_{de}\Omega_{de}=w_{de}\Omega_{de}\geq-1$. In this paper we study constraints on the dark energy models from the requirement of the NEC. We will show that with $\Omega_{de}\sim0.7$, $w_{de}
Comment: 9 pages, 6 figures